Lay Bet Liability Calculator
On a betting exchange, laying a selection means taking the bookmaker's side: you win the backer's stake if it loses and pay out at the agreed odds if it wins. Enter a lay stake, or the most you are prepared to lose, to see the liability, the net win after commission and the probability the lay needs to break even.
In one line: liability = lay stake × (odds − 1). A £10 lay at 4.0 risks £30 to win £10, or £9.80 after 2% commission.
Exchange odds are decimal and include your stake. Commission is charged on net winnings in a market; enter the rate on your own account. To lay off a bet you have already backed with a bookmaker, use the back-lay calculator instead.
Result
How a Lay Bet Is Settled
When you lay at 4.0 for £10, the exchange matches you with someone backing at 4.0 for £10. If the selection wins, the backer is paid £30 profit and that comes from you: your liability, which the exchange holds from your balance as soon as the bet is matched. If it loses, the backer's £10 is yours, less commission on the net winnings in that market.
Worked example: three ways to look at the same lay
Lay £10 at 4.0, 2% commission. Liability £30; net win £9.80; you risk £3.06 for every £1 you can win. The price implies a 25% chance; with commission, the lay breaks even only if the true chance is below (1 − 0.02) ÷ (4 − 0.02) = 24.62%. If you rate the selection at 20%, the expected value is 0.8 × £9.80 − 0.2 × £30 = +£1.84; at 25%, it is 0.75 × £9.80 − 0.25 × £30 = −£0.15. In liability mode, capping the loss at £50 at odds of 6.0 gives a lay stake of £50 ÷ 5 = £10.
A £10 lay across the odds
| Lay odds | Liability | Net win, 2% | Net win, 5% | Break-even, 2% | Break-even, 5% |
|---|---|---|---|---|---|
| 1.50 | £5.00 | £9.80 | £9.50 | 66.22% | 65.52% |
| 2.00 | £10.00 | £9.80 | £9.50 | 49.49% | 48.72% |
| 3.00 | £20.00 | £9.80 | £9.50 | 32.89% | 32.20% |
| 4.00 | £30.00 | £9.80 | £9.50 | 24.62% | 24.05% |
| 5.00 | £40.00 | £9.80 | £9.50 | 19.68% | 19.19% |
| 8.00 | £70.00 | £9.80 | £9.50 | 12.28% | 11.95% |
| 10.00 | £90.00 | £9.80 | £9.50 | 9.82% | 9.55% |
| 20.00 | £190.00 | £9.80 | £9.50 | 4.90% | 4.76% |
The win is the same £9.80 or £9.50 on every row; the liability is what changes. The break-even chance sits a little below the implied chance (25% at 4.0) because commission takes a slice of every winning lay. The back-side equivalent, a price's break-even win rate, is in the break-even odds calculator, and the way decimal odds map to probability is explained in how betting odds work.
Rules worth knowing before you lay
In-play, the price can move against you in seconds, and an unmatched lay may be matched at a moment you did not expect; exchanges let you cancel unmatched bets, not matched ones. In horse racing, a non-runner triggers a reduction factor on matched bets in the same market, the exchange's version of a Rule 4 deduction. In the UK, exchanges are licensed by the Gambling Commission like any bookmaker; check the licence before you deposit.
Frequently Asked Questions
How do you calculate lay bet liability?
Liability = lay stake × (lay odds − 1). Laying £10 at 4.0 means accepting a £10 bet from a backer at those odds: if the selection wins you pay out £30, which is your liability; if it loses you keep the backer's £10, minus the exchange's commission.
How do I work out the lay stake from a maximum liability?
Divide the liability by (odds − 1). To risk no more than £50 on a lay at 6.0, the lay stake is £50 ÷ 5 = £10. The calculator does this in liability mode, so you can set the most you are willing to lose and read off the stake to enter.
Is commission charged on the liability or on the winnings?
On net winnings in a market, not on the liability. If a £10 lay wins, a 2% commission costs 20p and you keep £9.80; at 5% you keep £9.50. If the lay loses you pay the full liability and no commission. Rates and discounts differ between exchanges, so use the rate on your own account.
When is a lay bet worth it?
Only when the selection is less likely to win than the lay price implies, after commission. The break-even probability for a lay is (1 − c) ÷ (odds − c). At 4.0 with 2% commission that is 24.62%: if you think the true chance is lower, the lay has positive expected value; if higher, it does not.
Why is laying a favourite cheaper than laying an outsider?
Because liability grows with the odds. Laying £10 at 1.5 risks £5, at 10.0 it risks £90 and at 20.0 it risks £190, for the same £10 maximum win. A lay of a long-priced runner wins often and loses rarely, but each loss can be many times the stake.
Laying means your possible loss is the liability, not the stake: look at the liability figure before you confirm, especially at long odds. 18+. If gambling stops being fun, see our responsible gambling resources.