Probability of Success Calculator
Evaluate your historical or backtested trading results using Win Rate, Risk–Reward, Break-Even Win Rate, Profit Factor and Trade Expectancy.
Win Rate vs Break-Even Win Rate
Trade Summary
What is Probability of Success in Trading?
In trading, Probability of Success refers to the percentage of historical or backtested trades that ended successfully according to the rules of a particular strategy.
This calculator uses your historical or backtested trade results to calculate the strategy’s historical Win Rate. It does not predict the outcome of the next individual trade.
1. Historical Win Rate
Win Rate shows the percentage of trades that were profitable in the sample entered into the calculator.
For example, if 60 out of 100 trades were profitable:
2. Historical Loss Rate
3. Break-Even Win Rate
Break-Even Win Rate is the approximate win rate required to achieve zero mathematical expectancy when the average winning trade and average losing trade remain constant.
For example, if the average winning trade is +2R and the average losing trade is -1R:
4. Average Risk–Reward Ratio
The calculator uses the average winning trade and average losing trade to estimate the average Risk–Reward relationship.
If the average loss is 1R and the average win is 2R, the average Risk–Reward is:
5. Trade Expectancy
Expectancy estimates the average amount of R that the strategy would mathematically expect to gain or lose per trade based on the historical inputs.
A positive expectancy means the historical combination of Win Rate, Average Win and Average Loss produces a positive mathematical expectation.
6. Profit Factor
Profit Factor compares the total gross profit generated by winning trades with the total gross loss generated by losing trades.
A Profit Factor greater than 1 means gross profits are greater than gross losses in the historical sample, before considering other costs and assumptions.
Total Trades = 100
Winning Trades = 60
Losing Trades = 40
Average Winning Trade = +2R
Average Losing Trade = -1R
Historical Win Rate:
60 ÷ 100 × 100 = 60%
Loss Rate:
40 ÷ 100 × 100 = 40%
Break-Even Win Rate:
1 ÷ (2 + 1) × 100 = 33.33%
Profit Factor:
(60 × 2) ÷ (40 × 1) = 3.00
Expectancy:
(0.60 × 2) − (0.40 × 1)
= 1.20 − 0.40
= +0.80R per trade
Important: Historical Probability Is Not a Prediction
A historical Win Rate of 60% does not mean that the next trade has a guaranteed 60% probability of success.
Market conditions can change, and future trade outcomes can differ significantly from historical or backtested results.
The reliability of the calculation depends on the quality, size and consistency of the historical sample and whether the trading rules remained consistent across those trades.
Transaction costs, brokerage, taxes, slippage, liquidity, execution differences and market gaps can also affect actual trading results.
⚠️ Disclaimer
This calculator is provided for educational and informational purposes only. It does not constitute investment advice, trading advice, financial advice, or a recommendation to buy or sell any security.
The Historical Win Rate shown by this calculator describes the results entered by the user. It is not a prediction or guarantee of future trading performance.
Stocks, derivatives and other financial instruments involve risk. Losses can occur. Always consider your own risk tolerance, financial situation and trading plan before making any investment or trading decision.