Lay Betting Calculator
Exchange lay stake, liability and profit versus a back bet.
How to Use This Calculator
- Input the back stake
- Input the bookmaker back odds
- Input the exchange lay odds
- Input the exchange commission rate (default 5%)
- Read the recommended lay stake, liability, and profit per outcome
Formula
Lay Stake = (Back Stake × Back Odds) / (Lay Odds - Commission Rate)
Liability = Lay Stake × (Lay Odds - 1)
Profit if Back Wins = Back Stake × (Back Odds - 1) - Liability
Profit if Lay Wins = Lay Stake × (1 - Commission Rate) - Back Stake
Frequently Asked Questions
Define a lay bet.
A lay bet is the inverse of a back bet — you bet against an outcome. If the selection loses you collect the backer’s stake minus commission; if it wins you pay out the winnings, your liability.
What is liability?
Liability is the most you can lose on a lay, equal to lay stake × (lay odds - 1). The exchange holds this amount until the event settles.
Which commission rate applies?
Betfair’s standard commission on net winnings is 5%; Smarkets is 2%. Some exchanges cut rates for high-volume users. Enter the rate tied to your specific account.
Why do lay odds exceed back odds?
Lay odds run slightly higher because the exchange must match backers to layers. That back-lay gap (the spread) reflects market efficiency — tighter spreads signal more liquid markets.