Trading Compound Interest Calculator

What does a 3% monthly return actually become? See the math.

Starting capital ($)

Periodic return (%)

Realistic active-trading targets: 0.5–2% monthly. Above 5% monthly is fantasy.

Compounding frequency

Time horizon (years)

Monthly addition ($, optional)

Add to the account each month. Set to 0 for pure compounding.

Ending balance

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Total contributions

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Total compound gains

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Effective annualised return

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The reality check most trading content avoids

"3% per month, compounded" sounds modest. Plugged in: $10,000 turns into $416,158 over 10 years. Over 20 years it becomes $17.3 million.

If anyone consistently achieved 3% monthly net returns, they would within a decade be one of the wealthiest people in the world. The reason this almost never happens: at scale, your own trades move the markets you're trading, and the strategies that work at $10,000 stop working at $1 million.

Realistic monthly active-trading returns for sustained periods are closer to 0.5-2%. Even that compounds powerfully: 1% monthly is ~12.7% annualised, which would put you near the top decile of retail traders consistently.

What this calculator is good for

Setting realistic goals. Plug in a target ending balance, work backwards to the return per period you'd need. See whether it's realistic.
Understanding compounding. Small differences in return compound to huge differences over decades.
Comparing scenarios. 1% monthly for 20 years vs. 5% monthly for 5 years — which is bigger? Try both.
Honest disillusionment. See what "10% monthly returns" claims would actually produce. Then look up the world's wealthiest traders. If their returns were that high, they'd be wealthier than them.

What the calculator does NOT account for

Taxes. Most trading gains are taxed at short-term capital gains rates. Subtract 25-40% from the ending balance for a realistic after-tax figure.
Drawdowns. The calculator assumes constant returns. Real trading has volatility — a 50% drawdown takes a 100% gain to recover. Account for this by running scenarios at 60-70% of your "average" return assumption.
Strategy decay. Most edges fade with adoption. The strategy returning 3% monthly today often returns 0% three years from now. Plan for periodic re-validation.
Inflation. Compound real returns, not nominal. Subtract 2-3% per year for inflation to get real purchasing power.

Reality framing. Buy-and-hold S&P 500 returns roughly 10% annually long-term. If you're trading actively and netting below 10% annualised after costs and taxes, you'd be better off buying SPY. SultraxAI publishes the signal accuracy so you can answer the question "is my edge real?" before betting decades on it.