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The compound interest calculator shows how your account grows when every profit stays in and keeps working. Set the starting balance, return per period, number of periods and top-ups — the calculator draws a chart and a growth table by month, week, day or year.
How to use the calculator
- Period — month, week, day or year. Return and number of periods use this unit.
- Starting balance.
- Return per period, % — e.g. 5% per month.
- Number of periods — e.g. 24 months.
- Top-up per period — the amount you add each period (can be 0).
Compound interest formula
Final = Balance × (1 + r)n, where r is the return per period (5% = 0.05) and n the number of periods. With top-ups the calculator repeats “add profit, add top-up” every period.
Example 1. 5% a month for 2 years
$1,000 × 1.0524 = $3,225. The account grew 3.2×. Without reinvesting it would be $1,000 + 24 × $50 = $2,200.
Example 2. The rule of 72
To estimate the doubling time, divide 72 by the return: at 5% a month about 14 months, at 3% — 24, at 10% — 7.
Growth of $1,000
| Monthly return | After 12 months | After 24 months | After 36 months |
|---|---|---|---|
| 2% | $1,268 | $1,608 | $2,040 |
| 3% | $1,426 | $2,033 | $2,898 |
| 5% | $1,796 | $3,225 | $5,792 |
| 10% | $3,138 | $9,850 | $30,913 |
Realistic returns and risk
Compounding numbers are easy to calculate and hard to achieve. Trading returns are uneven: winning months alternate with drawdowns, and a 30% drawdown needs +43% just to recover (see the drawdown calculator). For forecasts use the average return including losing periods — for example from a multi-year strategy test. The strategies below show such multi-year results.
Compounding in live trading
For profits to compound, the lot must grow with the balance. With risk set as a percentage it happens automatically: the lot size calculator or the free S4U Trade Panel for MT4/MT5 size each trade from the current balance.
FAQ
What’s the difference between simple and compound interest?
Simple interest is paid on the starting amount only. Compound interest is paid on the amount plus profits already earned, so growth accelerates.
What monthly return is realistic?
For manual trading with moderate risk, 2–5% a month averaged over a year is already a good result. Promises of a steady 30% a month usually end in a blown account.
How are top-ups handled?
Enter an amount in “Top-up per period” — it’s added after the profit in every period.
Can I model a negative return?
Yes, enter the return with a minus sign to see how the account shrinks under constant losses.
