Compounding Growth Calculator
Set your starting amount, a monthly return, and a number of years, and see what your capital could become when profits stay invested. Add a loss scenario to see what a losing stretch would cost you, and what it takes to earn it back.
How to read your results
Your projected capital account is what the starting amount grows into if every month’s profit stays in the account. Total profit is that end value minus what you put in. The capital multiple states the same thing as a ratio: 5.9× means every euro became €5.90.
Two outputs deserve a second look. Time to double tells you how long your money needs at the chosen rate (the back-of-envelope version is the rule of 72): about 23.5 months at 3% monthly, about 70 months at 1%.
And the monthly profit pair shows the compounding effect in income terms. At the defaults, month one pays €3,000 and month 60 pays €17,675, from the same percentage. The difference is your own retained profits going to work.
The compound growth formula, in theory
The math behind the calculator is one line: FV = PV × (1 + r)^n. Your starting capital (PV), multiplied by one-plus-the-monthly-return (r), raised to the number of months (n). €100,000 at 3% for 60 months: €100,000 × (1.03)^60 = €589,160.
That is the textbook version, and it lives in a frictionless world. Every month wins, nothing is withdrawn, nothing is charged. Real accounts pay fees and taxes, hit losing months, and get dipped into. The formula is the ceiling, never the forecast.
What it means for your money, in practice
Skip the algebra and keep this: your profits can earn profits, but only if you leave them alone. Each month’s gain joins the pile, and next month’s return is calculated on the bigger pile. Withdraw the gains and the pile never grows; the same 3% pays €3,000 forever. Leave them in and the pile does the heavy lifting. Slowly at first, then visibly.
Turn the reinvest toggle off in the calculator and you can watch the difference on your own numbers: €589,160 against €280,000 over five years, on identical inputs, with retention as the only variable separating the two figures the whole way through.
What a big loss does to your account
A big loss shrinks the pile every later month works from, and getting back costs more than what was lost:
| You lose | Left from €100,000 | Gain needed to get back |
|---|---|---|
| 10% | €90,000 | 11.1% |
| 20% | €80,000 | 25.0% |
| 30% | €70,000 | 42.9% |
| 50% | €50,000 | 100.0% |
The percentages are unforgiving because recovery is computed on the smaller base; the effect is severe enough that maximum drawdown has its own risk-measure literature. And losses arrive faster than projections assume: when the SNB removed the franc cap in January 2015, cross-currency liquidity vanished within minutes.
Set the loss slider to a strategy’s worst historical loss before believing any five-year number it produces. The full case for why capital protection decides the outcome is on the compounding portfolio growth page.
Running a strategy? Switch to the pool view
The second tab compounds a capital pool instead of a personal account: total strategy capital, gross monthly return, performance share, management fee. It shows the monthly profit the pool generates, the manager’s share of it, and what the pool becomes if profits are retained.
At €1M and 3% with a 20% share: €30,000 gross per month, €6,000 of it the manager’s. What running capital at size demands in return, from capacity through governance, is covered under scaling a trading strategy.
Before you trust any projection
The 3% default comes out of a year of editorial research into leveraged systematic trading: hard but achievable with risk management focus, and the lowest rate that compounds a portfolio to roughly 10× within seven years. The full reasoning is on the compounding portfolio growth page. Among the strategies we have assessed for The Review, even the strongest take losing months on the way to a rate like that.
For calibration: the median systematic program stops reporting within about 65 months of launch (Monash University CTA study), and annual attrition among CTAs runs near 23.5%, which means most return streams end before compounding gets interesting, and long before a five-year projection has had the chance to prove itself right or wrong. Durability first, rate second.
A fixed rate also hides the path. 2022 split the indices: the SG Trend Index returned about +27% while the S&P 500 lost about 18%, two return streams no constant-rate projection can represent. Fees compound against you too; a single percentage point of annual cost removes a five-figure sum from a €100,000 account over a decade.
So use the calculator the way it earns its keep: as a portfolio compounding calculator for the question “what would discipline be worth?”, with your own worst-case loss dialled in. For the general savings case, NASAA’s compound interest explainer covers ground this one deliberately leaves out.
FAQs
How do you calculate compound growth on a trading account?
Multiply starting capital by (1 + monthly return) raised to the number of months. €50,000 at 2% monthly for three years is €50,000 × (1.02)^36 ≈ €101,994. The formula assumes every profit stays in the account and no month loses money, so treat results as an upper bound.
How long does it take to double money at 3% a month?
About 23.5 months, from ln(2) ÷ ln(1.03). At 1% monthly the doubling time is roughly 70 months. Doubling time depends only on the rate, not on the starting amount, which is why the same strategy doubles €50,000 and €500,000 in identical time.
Why does the calculator include a loss input?
Because interruption is the main reason compounding projections fail. A loss shrinks the base every later month works from, and recovery requires a larger percentage than was lost: 25% after a 20% loss. Modelling growth without modelling the setback overstates every realistic outcome.
What is the difference between compounded and simple returns?
Simple returns are always calculated on the original capital; profits sit aside. Compounded returns are calculated on original capital plus retained profits, so the base grows. On €100,000 at 3% monthly over five years the two models end €309,000 apart.
This calculator is for illustration only. It does not represent a forecast, guarantee, or investment recommendation. Trading results vary and can be affected by fees, taxes, slippage, leverage, liquidity, drawdowns, and market conditions. Investor-protection basics: FINMA’s practical tips.