Free tool

Lay bet calculator

Backing at the bookmaker and laying the same selection at an exchange? Enter your numbers to get the exact lay stake, your liability, and what you keep whether the selection wins or loses. Toggle between a normal (qualifying) bet and a free bet (stake-not-returned).

Back stake (£) Back odds (decimal) Lay odds (decimal) Exchange commission (%) Mode

How laying works

On a betting exchange you can lay a selection — betting that it will not win, acting like the bookmaker. If you back the same selection at a bookie and lay it on the exchange, the two bets cancel out so you get a near-identical result whichever way it goes. That's the mechanic behind matched betting: the small guaranteed loss on a qualifying bet is the price of unlocking a free bet, and the free bet is where the profit comes from.

Lay stake (normal): (back odds ÷ (lay odds − commission)) × back stake. For a free bet (SNR) your own stake isn't returned, so the winnings you're matching are smaller: ((back odds − 1) ÷ (lay odds − commission)) × back stake. Your liability — the amount the exchange holds if the selection wins — is (lay odds − 1) × lay stake.

The closer your lay odds are to your back odds, the smaller your qualifying loss. Commission is charged only on net exchange winnings, which is why it nudges the lay stake down slightly. This is a returns calculator, not a tip — it tells you the maths, not whether to bet. Accounts do get limited over time, so treat any edge as finite.