What win probability do I need for this trade to break even?
Your break-even probability is the price plus your costs, expressed as a win rate. At $0.43 with 0.4% fees, 0.2% slippage and $1 of flat costs on a $250 stake, you need to win 43.43% of the time, not 43%.
The calculator compares that line with your own estimate and shows the highest price your estimate can still support.
- Best for
- Checking if a market price still leaves positive expectancy
- Primary output
- Break-even win probability after costs
- Use before
- Any trade where friction may erase a small edge
Key points
- Turns price and costs into the win rate you need
- Shows how far your estimate clears that line
- Finds the highest price your estimate can support
Method and assumptions
Why the price is not your break-even line
Comparing your probability with the price is a good first filter, but costs move the break-even line above the price. Fees and slippage raise what you pay and lower what you collect.
The thinner the edge, the more this matters. A trade that looks a point ahead of the price can be behind the real break-even line.
- The price is only the starting reference
- Fees and slippage raise the line
- Flat costs matter most on small stakes
- Thin edges disappear first
How to use the break-even calculator
Enter the price you expect to pay and the stake you plan to use. Flat costs are spread over the stake, so a smaller stake needs a higher win rate.
Then compare the break-even line with your estimate. The gap between them, in percentage points, is your buffer.
- Enter price, stake, and your estimated win probability.
- Add fees, slippage, and flat cash costs.
- Compare the break-even line with your estimated probability.
- Check the maximum price your estimate can still justify.
Worked break-even example
A contract trades at $0.43 and you plan to stake $250. Costs total $2.50, so you collect $328.90 net if you win and lose $252.50 if you lose. That puts break-even at 43.43%.
With a 56% estimate, your buffer is 12.57 points, and your estimate supports paying up to $0.554. At a price of $0.56, the trade would no longer clear your own estimate.
- The buffer says more than the price alone
- The maximum price makes a natural limit price
- A worse fill can turn a clear trade into a loss
Break-even mistakes to avoid
The common ones are comparing your estimate with the price instead of the break-even line, and entering a stake that does not match the order you will send.
Another is treating a pass as proof. A trade that clears break-even by a point or two still rests on an estimate that is rarely that precise.
- Comparing estimate to price but not to real break-even
- Ignoring fixed costs on small trades
- Using optimistic fee or slippage assumptions
- Treating a tiny buffer as if it were robust edge
Sources and assumptions
Frequently asked questions
What is the difference between market implied probability and break-even probability?
Market implied probability comes from price alone. Break-even probability is the higher win rate you need after fees, slippage, and flat costs are included.
Why does the tool show a maximum price for my estimate?
It tells you the highest contract price that still preserves your current expected edge after costs. That is useful when deciding whether to chase a moving market.
Can a trade clear break-even and still be a bad trade?
Yes. If the probability buffer is tiny, the estimate is weak, or the market structure is risky, clearing break-even alone is not enough.
Should I use this together with Kelly sizing?
Yes. First check whether the edge survives costs, then use a sizing tool to decide how much of your bankroll deserves exposure.