Compounding calculator for traders
What a monthly return does to a balance over time, with deposits or withdrawals — arithmetic only, not a forecast.
How the balance is calculated
The calculator applies one rule month after month: the balance grows (or shrinks) by the monthly return, then the monthly deposit is added — a negative deposit is a withdrawal:
balance next month = balance this month × (1 + monthly return) + monthly deposit
It runs for 1 to 120 months and shows the final balance, the total of your deposits, the total gain — the final balance minus the starting balance and the deposits — and a table of the balance at the end of each year.
A worked example
Start with $10,000 and a monthly return of 1% — an input for the arithmetic, not an expectation — with no deposits. After 12 months the balance is 10,000 × 1.01¹² = $11,268.25, a gain of $1,268.25: slightly more than twelve times 1%, because each month earns on the previous months' gains.
Add $200 at the end of every month and the year ends at $13,804.75: $10,000 to start, $2,400 of deposits and $1,404.75 of gain. Change the return to −1% with no deposits and the same $10,000 becomes $8,863.85 — the rule works the same way downwards.
What one bad month does
The widget also shows what a single −10% month in the middle of the period does. In the example above, replace one of the twelve months with −10%: 1.01¹¹ × 0.90 = 1.0041, so $10,000 ends the year at about $10,041 instead of $11,268. Eleven positive months barely make up for one bad one. It is the same asymmetry the drawdown recovery calculator measures: a 10% loss needs an 11.1% gain to undo.
Why a steady monthly return is only an assumption
Real months vary: some are flat, some are losing, and once deposits or withdrawals are involved the order of good and bad months changes the result too. A fixed monthly percentage is a modelling assumption, not something any strategy delivers. Use the calculator to see how compounding, deposits and withdrawals interact, or how much a losing month costs over a year — not to set a target or to judge what a strategy will earn.
Where honest inputs come from
If you want to test a number, take it from your own history rather than from a promise: the average and the spread of your monthly results, your win rate and average R, and your largest drawdown. The risk-reward calculator turns win rate and R into expectancy per trade, and profit factor and maximum drawdown explain two numbers worth tracking next to any return. A negative deposit models taking a monthly income from the account, and the year-by-year table shows whether the balance holds up under the assumption you entered.
Frequently asked questions
Is a steady monthly return realistic?
No trading result is steady. Monthly returns vary, losing months are normal, and past results do not predict future ones. The calculator shows arithmetic under an assumption you choose; it is not a forecast or a target.
How are deposits and withdrawals handled?
The deposit is added at the end of each month, after that month's return. A negative number is treated as a withdrawal of that amount every month.
Why does one −10% month matter so much?
Because the loss is taken from a larger balance and the gains that follow are earned on a smaller one. In the example on this page, one −10% month wipes out almost a whole year of 1% months.
Is my data sent anywhere?
No. Everything is calculated in your browser.