Free trading calculators
Six free calculators for the questions that decide whether a trading plan survives: how large to trade, how often a losing run arrives, whether a win rate is real, and what a prop firm's rules do to it. They run in your browser, need no account, and use the same tested maths as the STS Trading terminal.
Last updated 30 September 2026.
- Prop challenge pass probability
Your win rate and risk against a challenge's target, daily limit and maximum loss.
- Daily drawdown calculator
The risk per trade that keeps a losing run inside a daily loss limit.
- Position size calculator
Lots from your balance, your risk and your stop, rounded the way a broker rounds.
- Win rate confidence calculator
The range your real win rate probably sits in, and whether it clears break-even.
- Risk of ruin calculator
The chance of a deep drawdown at the size you trade, from your own record.
- Break-even win rate calculator
The win rate a reward to risk needs, and how many trades prove you beat it.
Nothing you type into a calculator is stored or sent anywhere.
A calculator shows what follows from the numbers you enter. It is not a forecast and not personal financial advice. Trading carries risk and you can lose money.