Paperball Finance

Paperball Finance is a web-based portfolio backtester: it runs portfolios of ETFs, funds and stocks on historical prices — after costs, distributions and taxes — and simulates withdrawal plans with Monte Carlo. It is operated by 121 Apps GmbH in Munich and hosted in Germany.

Information as of:

Paperball Finance: Key facts

Type
Web application for portfolio backtests, withdrawal plans and Monte Carlo simulations
Hosting
Server in Leipzig, Germany; encrypted backups in Amsterdam
Securities
ETFs, funds, bond funds, stocks, REITs, ADRs and GDRs, each with price history: a choice of more than 80,000 securities, plus users' own prices from CSV, Excel or ODS files
Tax mechanics
Germany, Austria, Switzerland, United Kingdom, France, United States, Netherlands and Sweden
Languages
Dansk, Deutsch, English, Español, Français, Italiano, Nederlands, Norsk, Polski, Português and Svenska
Legal framework
Mathematical analysis tool; no investment advice, investment brokerage or portfolio management within the meaning of the German WpIG/WpHG

Paperball Finance: What it is

Paperball Finance does not try one allocation but every allocation of the selected securities in fixed steps, and sorts them by metrics such as the Sharpe, Sortino or Calmar ratio. Each allocation is calculated in five rebalancing variants: never, monthly, quarterly, semi-annually and annually.

On top of that come withdrawal plans for retirement and Monte Carlo simulations that build 10,000 possible paths from a portfolio's real monthly returns. All portfolios are virtual: no securities are bought or sold and no money is invested.

Paperball Finance: How it calculates

Calculations run on historical daily prices, with everything that changes the return of a real portfolio:

  • Costs: order fees (fixed, percentage, with minimum and maximum), front-end loads per security and an annual custody fee as a percentage of the portfolio value. A fund's ongoing charges (TER) are already included in its price and are not deducted again.
  • Distributions: every distribution counts on the ex-dividend date — the first trading day on which the security trades without entitlement to the distribution — and is taxed. What happens to it next is your choice: by default it is ignored and shown as a metric of its own. When reinvested, the backtest uses it to buy units of the same security, without an order fee and without a front-end load. With a savings or withdrawal plan it can instead pay the withdrawals from the cash account or go into the liquidity buffer.
  • Taxes: the tax mechanics of 8 countries. The calculation covers taxes on capital gains and distributions and, depending on the country, also a partial exemption for funds (Teilfreistellung), an annual tax-free allowance, a reduced rate after a holding period, wealth tax and, for Germany, the advance lump-sum tax on funds (Vorabpauschale). In addition, there are tax-advantaged accounts such as ISA, Roth IRA or ISK. The user sets the tax rates; non-binding example values per country can be adopted. The result is an approximation, not tax advice.
  • Rebalancing: on each rebalancing date, Paperball Finance sells every position whose value exceeds its target value by more than 1 % of the portfolio value, down to the target value. The proceeds go to the positions that are more than 1 % below their target value; if none is that far below, to all underweight positions – in each case in proportion to their distance from the target value. Sales incur an order fee and tax on the gain realised; purchases incur an order fee and a front-end load.
  • Savings plan: in the backtest, Paperball Finance invests one instalment on the first trading day of each savings period, optionally with an annual increase in the instalment and with separate savings plan fees. The savings phase can be followed by a withdrawal plan in the same run.
  • Withdrawal plan: a fixed amount adjusted for inflation or a percentage of the value, monthly to annually; with a fixed amount, optionally with an interest-bearing cash buffer.
  • Period: a backtest starts no earlier than the day from which all selected securities have continuous daily prices. The security whose price history begins latest determines the start; a shorter period can be selected. Paperball Finance does not extend short price histories using index or substitute series; users' own price files that reach further back can extend them. Monte Carlo on asset mixes calculates only within the period that is covered by all building blocks with a price history of their own.
  • Currency: Paperball Finance calculates backtests and Monte Carlo simulations in euros. Prices in other currencies are converted for each day at the reference rate of a central bank that was published on that day or most recently before it. Before 1999, Paperball Finance calculates via the Deutsche Mark: with the daily rates of a central bank, converted at the fixed rate of 1.95583 Deutsche Mark per euro; these are available from 1971 for the US dollar, pound sterling, Swiss franc, yen, Canadian dollar and the Scandinavian currencies. For the US dollar, the fixed parities of the Deutsche Mark apply from October 1949 to 1970: 4.20, from March 1961 4.00 and from October 1969 3.66 Deutsche Mark per dollar; during the float in autumn 1969, the last rate before it applies. There is no currency hedging: return, volatility and drawdown include exchange rate movements from the perspective of a euro investor. If an exchange rate is missing or the currency of a security is unknown, the backtest does not start. Results can be displayed in other currencies: the finished euro amounts are then converted at the exchange rate on the start date and on the end date; the metrics in per cent remain unchanged. The exception is the years before November 1949 in the building block US equities since 1871: from December 1924 to June 1941 it calculates via the Reichsmark (monthly averages of New York rates); before and after that there is no usable exchange rate, so its return counts in dollars there, without exchange rate movements. If US equities since 1871 and German equities since 1871 are in the same asset mix, both count in purchasing power in the months without an exchange rate between mark and dollar. The building blocks global equities since 1871 work the same way: until July 1914 via the fixed gold parity, from December 1924 to June 1941 via the Reichsmark (sterling via its dollar rate), and in the months without an exchange rate between mark and dollar each country in purchasing power. In an asset mix with German or global equities since 1871, US equities count via the gold value of the dollar (the dollar rate of sterling) until December 1878, because the dollar only returned to gold in 1879.
  • Metrics: annual return (CAGR), volatility, maximum drawdown and the longest time without a new high (in trading days), Sharpe, Sortino, Calmar, Sterling and Martin ratios, Ulcer index, plus beta and alpha against a selectable benchmark. The Sharpe ratio, the Sortino ratio and alpha are calculated against a risk-free rate that the user sets. The Community-Backtests calculate all portfolios to a uniform standard: without taxes and fees, with a risk-free rate of zero and starting no earlier than a uniform cut-off date. This makes the metrics of the Community-Backtests comparable with one another. The benchmarks include distributions (total return) and are converted into euros.
  • Monte Carlo: two calculation methods are available. “Drawn anew” (default): from the historical monthly returns, Paperball Finance draws pieces of consecutive months at random and with replacement and joins them into 10,000 possible paths – a historical block bootstrap. The default is pieces of 12 months; the piece length can be set from 1 to 60 months or made random, 12 months long on average (stationary bootstrap after Politis and Romano). Within a piece, crisis and recovery stay together; no normal distribution is assumed. Optionally, the return can be set cautiously: every monthly return is scaled down by the same factor until the average return matches a more cautious value – suggested from long equity and bond series, compared after inflation, or chosen freely; it is never raised. “Real start years”: without randomness, Paperball Finance plays the plan through in real order from every January of the price history from which the whole term still fits in – a historical simulation with rolling windows, using real prices only and only with at least 20 start years. Both methods only assemble what occurred in the price history; they cannot generate market phases outside the data. No calculation is run with a price history shorter than 5 years, and with one shorter than 10 years the interface shows a warning. The calculation covers savings and withdrawal phases, optionally with tax under the same settings as in the backtest, approximated per path. As the sustainable amount, Paperball Finance shows the highest withdrawal that would have lasted until the end of the term in at least 90 % of the paths.
  • Inflation: Where the price history starts in February 1871 or later, Paperball Finance takes inflation from the same months as the returns, in the currency in which the returns count: official German consumer prices from November 1949, the cost-of-living index of the German Reich from December 1924 to June 1941, and US consumer prices in the other months before that – without a euro or Reichsmark exchange rate, returns count in dollars there. If it starts earlier, a fixed rate applies. If an asset mix contains German or global equities since 1871, the German cost-of-living index applies until October 1949; from November 1918 to January 1924 this building block counts in purchasing power, without inflation. The building blocks global equities since 1871 count in purchasing power, without inflation, in the months without an exchange rate between mark and dollar.
  • Building blocks: instead of a saved portfolio, a Monte Carlo simulation can calculate an asset mix of building blocks. Building blocks are series for equities, bonds and gold, the money market rate, a fixed interest rate and, if desired, the securities the user has saved. The Bund building blocks are not traded funds: Paperball Finance calculates them from the yields that a central bank has published monthly since 1972, as a zero-coupon bond with a constant remaining maturity of 2, 7 or 10 years that is bought anew every month. The building block for US Treasuries is calculated in the same way: from the yields on ten-year US Treasury bonds that have been published daily since 1962, as a bond with a semi-annual coupon and a constant remaining maturity. Two building blocks go back further than any fund: German equities since 1954 from an academic series (all shares in the top Frankfurt segment) and US equities since 1926 from an academic data collection (the entire US stock market); from 2014 and 1993 respectively, they are continued with traded ETFs. The building block for German government bonds since 1956 is calculated in the same way: from the yield on ten-year German government bonds published monthly by an international organisation, as a bond with an annual coupon; for the years before 1972 it is probably based on the average yield on German bonds outstanding, an average across all remaining maturities. The longest series is US equities since 1871: until 1926 estimated from two research data collections (monthly averages of a broad index and month-end prices of individual stocks), then the same series as US equities since 1926; before November 1949 it calculates via the Reichsmark from December 1924 to June 1941 and otherwise in dollars, without a currency effect, because there is no usable exchange rate. Gold goes back to 1960: until 2009 the gold price in dollars from the commodity prices of an international organisation (monthly averages), converted into euros, from 2010 Xetra-Gold. German equities since 1871 go back just as far: until 1953 an index of German blue-chip stocks with dividends from a research study (monthly averages), then the same series as German equities since 1954; from August 1914 to October 1918 the stock exchange was closed, and from November 1918 to January 1924 the return counts in purchasing power. Global equities since 1871 are estimated, in five versions: like the MSCI World (until 2007 70 % US, then the iShares MSCI World), with a fixed 30 or 50 % US or US only (from 2008 from the SPDR S&P 500 ETF and the iShares MSCI EAFE), and historically weighted by the market value of the countries at the time (from 2008 the iShares MSCI World). Until 2008 they are made up of US, British, German, French, Italian and Japanese equities. The British equities come from a central bank's collection of historical economic data, without dividends, using the dividend yield of US equities instead; for France, Italy and Japan there are only annual figures from a research data collection, spread over twelve months using the pattern of the British months. The selection for new asset mixes offers the longest series per asset class – the ten-year German government bond as one series since 1956, until August 1972 from the international organisation's yield, then from the yield curve –; country series and individual index ETFs keep working in saved asset mixes and as benchmarks in the backtest.
  • Data: Paperball Finance obtains prices, distributions and master data of the securities from a licensed market data provider. The benchmarks are ETF series built from these prices in which the distributions are reinvested (total return). Sector and country breakdowns of funds come from the holdings lists of the fund companies, supplemented by AI research via web search. Exchange rates and money market rates are reference values of central banks, bond yields come from central banks and an international organisation, and the long equity series from academic research. Users can upload their own prices as CSV, Excel or ODS files.

Paperball Finance: Made & hosted in Europe

Paperball Finance is developed and operated by 121 Apps GmbH in Munich. The application and database run on a server in Leipzig, backups are stored encrypted in Amsterdam, and emails are sent by a service based in Paris. The GDPR applies.

Wherever an equivalent European technology was available, it was chosen. The table lists every service that is involved in operations or supplies data, including services outside the EU. For each service it states which user data it receives.

ServicePurposeProvider's seatUser data
121 Apps GmbHDevelopment and operationMunich, GermanyController under the GDPR
Alfahosting (dogado)Server and databaseHalle (Saale), GermanyAll application data, data centre in Leipzig
Backblaze B2BackupsUSAEncrypted only, stored in Amsterdam
Plausible Analytics (self-hosted)Visitor statistics without cookiesNo external provider; runs on the application's server in Leipzig, GermanyPage visited, referring page, browser and device type; the IP address is used only for a hash that changes daily and for assignment to a region, and is not stored
BrevoEmails and confirmation codes by text messageParis, FranceEmail address; for text messages, the phone number
Stripe (Link)Payment, invoicing and VATDublin, Ireland (group based in the USA)Email address, user name or account name where available, and internal identifiers for the customer account and the invoice. The user enters card and bank account details directly with Link (Stripe); Paperball Finance does not receive them.
DeepLTranslation of the interfaceCologne, GermanyNone
Anthropic (Claude)Researching master data and sector and country breakdowns of funds by web search; translating the interfaceUSANone
Licensed market data providerPrices, distributions and master data of securitiesOutside the EUNone
Fund companiesPublished holdings lists of their funds for the sector and country breakdown; published master data such as costs and risk ratingInside or outside the EU, depending on the fund companyNone
Central banksReference rates for currency conversion, money market rates, government bond yields, and British share prices, sterling exchange rates and consumer prices from 1871Germany and USANone
Open exchange rate interfaceProvides a central bank's reference rates for retrievalOpen-source project; no operator with a registered seat is statedNone
German, European and international statistical bodiesGerman consumer prices for inflation from the price history in Monte Carlo, the yield on ten-year German government bonds from 1956, and gold prices from 1960 to 2009 for the long gold building block, plus the market value of the countries from 1975 for the historically weighted global seriesGermany, France, Luxembourg and USANone
Academic data collectionsMonthly returns of US and German equities from 1871 and annual returns of French, Italian and Japanese equities for the long equity building blocks in Monte Carlo, plus the market value of the countries 1913–1970 for the historically weighted global seriesGermany and USANone
121assist (121 Apps GmbH)Support chat on the websiteMunich, GermanyWhat you type into the chat, the language, the address of the page and of the page before it, and a random identifier in your browser. No data from your Paperball account.
OpenAIAnswers in the support chat: search in the explanatory texts and language modelUSAWhat you type into the chat, together with matching passages from Paperball’s explanatory texts
Google, Microsoft, LinkedIn, FacebookSign-in, if chosenUSAName and email address, only with this sign-in

Paperball Finance: Who it is made for

Ambitious DIY investors with professional standards

People who build their own portfolio of ETFs and stocks and want to test it with metrics that are also used in professional portfolio analysis. For this, Paperball Finance calculates every allocation of their securities in fixed steps — with costs, taxes and rebalancing.

Typical questions

  • How would my portfolio have performed in the past?
  • How large would the maximum drawdown have been — and how long would the recovery have taken?
  • Where would my portfolio's allocation have ranked among all allocations of the same securities?

FIRE: financial independence, retire early

Anyone who saves for a long time in order to stop working early runs the saving phase and the withdrawals in one go — in the Monte Carlo simulation over 10,000 possible paths, with a target wealth and amounts in today's money.

Typical questions

  • In how many simulated paths would I have reached my target wealth?
  • What savings rate would my plan have needed to work in 90 % of paths?
  • Would the portfolio then have supported withdrawals over 40 years or more?

Retirement & withdrawals

Anyone who wants to live off their own portfolio in retirement or during a career break runs a withdrawal plan — in the backtest with the actual sequence of years and in the Monte Carlo simulation over 10,000 possible paths.

Typical questions

  • Would my portfolio have supported an annual withdrawal of €40,000?
  • In how many paths would the money have run out before the end?
  • What would a cash buffer have achieved in weak years?
  • How would the result have changed at a 3, 4 or 5% withdrawal rate?

Financial advisors

Paperball Finance is aimed at financial advisors and financial planners who run separate portfolios and scenarios for each client. Each client account has its own login, and its data stays separate from the other accounts. On request, PDF reports carry the advisor's own logo, accent colour and company name. Which of these features are included depends on the plan. The advice itself stays with the advisor.

Typical questions

  • How would my clients' portfolios have developed in crisis years?
  • Would my client's withdrawal plan have held up over 30 years?
  • How do I present the result in a report with my logo?

Businesses and integrations

Paperball Finance is also aimed at robo-advisers, finance portals and fintechs that want to use the service from their own systems. Via the MCP server (Model Context Protocol), an interface for programs and AI assistants, their systems start backtests and Monte Carlo simulations and retrieve results. A webhook notifies a company's own system that a backtest has finished; there is none for Monte Carlo simulations. Widgets embed saved portfolios and rankings from the Community-Backtests in third-party websites. Paperball Finance does not currently have a public REST API.

Typical questions

  • Can we start backtests and Monte Carlo simulations from our own system?
  • How do we embed portfolios and rankings in our portal?

Paperball Finance: Features per plan

FeaturePlusFreeProTeamProfessional
Credits and limits
CreditsYou get one-time starter credits for free, valid for 12 months. With a subscription, new credits arrive every month and expire at the end of the month, with no rollover. In the plans for accounts, it is one balance for the whole account, which you distribute as a shared pool or in fixed shares.15,000 per month20,000 one-time60,000 per month200,000 per month600,000 per month
Backtest, simulation or updateWhat a run costs, the same in every plan: a backtest 1,000 credits, a Monte Carlo simulation 1,000, a day of updates 1,000. An update brings the Watchlist and saved portfolios up to date once a day, no matter how many securities they contain; without new prices it costs nothing.1,000 credits1,000 credits1,000 credits1,000 credits1,000 credits
Buy more creditsPacks of 5,000 to 130,000 credits, from €5, that never expire — the bigger the pack, the cheaper each credit. The monthly allowance is used first, then the starter credits, then purchased credits.includedincludedincludedincludedincluded
SeatsHow many people work in the account, including you. Open invitations count too.111525
Client accountsFor advisors and family offices: a separate account with its own login for each client. You switch into it without a password; each client's data stays separate.not includednot includednot included525
Securities per backtestHow many securities you select at once for a backtest to find their allocation with the highest metrics. You see how many allocations that makes before you start; if the number is above the upper limit, the backtest doesn't start.8881215
Step size of the weightings in a backtestThe finest step a backtest uses to split the weights. At 5% it checks 21 values per security (0, 5, 10 … 100%); coarser is always possible.5 %5 %5 %5 %5 %
Your own backtest setsHow many backtest sets of your own you can create — e.g. “World ETFs”, “Tech stocks”, “Bonds”. The test securities are available on top and don't count.10101050100
Saved resultsEvery backtest saves its result. Once you reach the limit, a new backtest only starts after you delete an old result.10020100100100
Saved portfoliosPortfolios you keep from a backtest result in “My portfolios”.100100100100100
Securities in the WatchlistHow many securities your Watchlist holds. The test securities and securities from folders that others in the account share with you don't count.1,0002002,0002,0005,000
API calls per monthWith an API key you connect Paperball to an AI assistant that supports the Model Context Protocol (MCP). It can then start backtests for you, look up results and add securities and prices. This many calls are included per month.25,0001,00025,00050,000100,000
Calculations
Backtest with taxes and feesEvery backtest factors in order fees, distributions and your country's tax rules, and finds the allocation of your securities with the highest metrics.includedincludedincludedincludedincluded
Monte Carlo on your own portfolios10,000 possible paths are built from real monthly returns — for your saved portfolios, an asset mix of your own or a portfolio from the Community-Backtests, with your starting capital, savings plan and withdrawal plan, and with tax if you want.includedincludedincludedincludedincluded
Savings and withdrawal planFactor in regular contributions and withdrawals — a fixed amount with inflation adjustment or a percentage of the value, after selling costs and tax, optionally with an interest-bearing liquidity buffer.includedincludedincludedincludedincluded
Update the Watchlist and portfolios, even dailyBring Watchlist folders and portfolio lists up to date daily, weekly or monthly, with an optional e-mail. A day of updates costs 1,000 credits, for the Watchlist and portfolios together.includedincludedincludedincludedincluded
Prices and distributions from a fileUpload your own prices from a CSV, Excel or ODS file, and store your own distribution by sector and country for a fund.includedincludedincludedincludedincluded
Results and access
Excel and PDF exportSave results and portfolios as an Excel or ODS file, and as a print-ready PDF report with portfolios, metrics and the list of securities.includedincludedincludedincludedincluded
Report by e-mailAfter every scheduled update, Paperball sends you a report on your Watchlist folders and portfolio lists if you wish.includedincludedincludedincludedincluded
Community-BacktestsView the public Community-Backtests and show your own portfolios there — or keep your profile private.includedincludedincludedincludedincluded
API and AI assistantsCreate API keys and connect AI assistants such as Claude or ChatGPT to Paperball.includedincludedincludedincludedincluded
For clients and teams
Calculate for clientsCalculate for clients instead of just for yourself: create client accounts and label backtest sets with a client's name.not includednot includednot includedincludedincluded
PDF with your own logoFor advisors and family offices: PDF reports with your logo, your accent colour and your company name in the footer.not includednot includednot includedincludedincluded
Shared folders and credit poolInvite colleagues, share Watchlist folders and calculate from a shared credit pool, used as one pool or split into fixed shares per person.not includednot includednot includedincludedincluded
Overview of all clientsOne page with all client accounts and how many backtest sets, backtest results and portfolios each one has.not includednot includednot includedincludedincluded

Quantities and features per plan come from the current plan catalogue; prices are on the pricing page.

Paperball Finance: Scope and distinctions

What Paperball Finance is not

  • No investment advice, investment brokerage or portfolio management within the meaning of the German WpIG/WpHG; there are no buy, sell or hold recommendations.
  • Not a broker, bank or robo-adviser: no securities are traded, no custody account is held and no assets are managed.
  • Not a paper trading account for practising orders: Paperball Finance calculates portfolios over whole periods, not individual purchases.
  • Not a forecast: backtests and Monte Carlo simulations evaluate historical prices. The ranking of the allocations by a metric applies only to the period calculated. When a very large number of allocations are compared on the same price history, the top of the ranking shows what happened to fit exactly that history (overfitting). The more allocations are compared, the greater the share of chance at the top of the ranking. Past performance is not a reliable indicator of future performance.
  • Not tax advice: the tax mechanics are an approximation using rates that users enter themselves.

Not to be confused with

paperball.news
A news service under the same brand and from the same operator — with its own application and its own database. Paperball Finance contains no news.
paperball.ai
An AI workplace platform for companies from the same operator — unrelated to securities or backtests.

Paperball Finance: Frequently asked questions

How much does Paperball Finance cost?

The “Free” plan is permanently free and needs no payment details. Anyone who signs up gets 20,000 starter credits, valid for 12 months. Users can pick their own securities in every plan: more than 80,000 by ISIN or ticker, plus their own prices from files. The plans differ in monthly credits and in whether a team and client accounts are included. Cost in credits per run: backtest 1,000, Monte Carlo simulation 1,000, one day of updates 1,000. More credits come with a subscription (Plus, Pro, Team and Professional) or separately from €5; credits bought separately never expire. Prices are on the pricing page and include VAT.

Does Paperball Finance give investment recommendations?

No. Paperball Finance shows how allocations would have developed in the past and does not recommend what anyone should buy or sell. Everyone makes their own investment decisions.

Where is Paperball Finance's data stored?

The application and database of Paperball Finance run on a server in Leipzig, Germany. The backups are stored encrypted in Amsterdam. The operator is 121 Apps GmbH in Munich; the GDPR applies. Some data goes to further services, for example for payment and for sending emails; the table of services on this page lists each one with its seat.

Are backtests in Paperball Finance public?

No. Backtests stay private until someone switches on publication in the Community-Backtests themselves — and it can be switched off again at any time.

Does Paperball Finance have an API?

Paperball Finance does not currently have a public REST API. Programs and AI assistants gain access via the MCP server (Model Context Protocol) and authenticate with an API key. When a backtest has finished, Paperball Finance can report this as a signed webhook to an HTTPS address of the user. Saved portfolios and rankings from the Community-Backtests can be embedded as a widget in third-party websites.

Can an AI assistant use Paperball Finance?

Yes. Via the MCP server (Model Context Protocol), Claude, for example, can use an API key to start backtests and Monte Carlo simulations and retrieve results. How many calls per month are included depends on the plan.

Paperball Finance: Further information