Trading Compound Interest Calculator
Compound a starting balance at a fixed return, monthly to daily, with optional deposits — and see what one drawdown does to the curve.
What it does
- Any period you actually think in — Monthly, weekly, daily trading days, quarterly or yearly. Traders quote returns per month; the calculator should not force you into years.
- Deposits included — Add a fixed amount each period. It separates what you paid in from what the returns produced, which is usually the more interesting number.
- The annual equivalent — Shows the compound annual rate your inputs imply. This is where 3% a month stops sounding modest.
- It argues with you — Every result carries what a single drawdown would do to it, and how long the same return needs to recover. The curve is the easy part.
Why the number surprises people
Three per cent a month sounds reasonable. Modest, even. Compounded it is about 43% a year, and over three years it more than doubles the account.
That is the useful thing a compound calculator does: it converts a rate that sounds achievable into a total that plainly is not, and lets you decide which of the two you believe.
The curve is not the plan
Every compound projection makes one assumption that never holds: that each period returns exactly the same amount. Real returns arrive in clumps, with losing stretches in between, and the curve is far more fragile to that than it looks.
A 30% drawdown does not need a 30% gain to recover. It needs about 43%. At 3% a month that is roughly twelve months of perfect trading to get back to where you already were — and the calculator says so under every result, using your own numbers rather than a generic warning.
What it is good for
Setting expectations you can hold to. If your plan needs 8% a month to reach a number by a date, the calculator will show you that, and the honest conclusion is usually that the date is wrong rather than the plan.
It is also the fastest way to see how much of a projected balance is your own deposits rather than trading returns. Frequently, most of it.
What it is not
It is not a forecast, and it does not know anything about your strategy. It is arithmetic on an assumption you supplied. The assumption is the part worth arguing about.