Lay Bet Calculator 2026
Work out the exact lay stake, liability and profit for a back-and-lay bet on any exchange. Covers normal qualifiers, stake-not-returned and stake-returned free bets, underlay and overlay weighting, and Betfair, Smarkets or Betdaq commission.
Lay bet calculator
A normal real-money back bet, usually placed to unlock a promo. You accept a tiny loss.
Same profit whichever side wins. The standard matched-betting lay.
Lay bet result
$9.64
$30.84
Held by the exchange until the bet settles-$0.84
Both outcomes are matched within a cent, so this is a clean equalised lock.
How lay betting works
Back at the bookmaker
Place your back bet on a selection, usually to trigger a promo or use a free bet. You win if the selection wins.
Lay on the exchange
Bet against the same selection on an exchange. You win if it loses, and you post a liability to cover it.
Size the lay
The calculator returns the exact lay stake so both outcomes settle to the same profit, after commission.
Bank the result
Whichever side wins, you collect the shown result. A free bet turns into guaranteed profit; a qualifier costs a tiny loss.
The lay betting math
Every number this calculator returns, in plain arithmetic.
Lay stake (qualifier)
$10 at 4.00 back, 4.20 lay, 5% comm: 40 / 4.15 = $9.64.
Liability
$9.64 lay at 4.20: 9.64 × 3.2 = $30.84 held.
Lay stake (SNR free bet)
$10 SNR at 5.00, 5.20 lay, 5% comm: 40 / 5.15 = $7.77.
Lay stake (SR free bet)
$10 SR at 5.00, 5.20 lay, 5% comm: 50 / 5.15 = $9.71.
Lay betting, explained
A lay bet backs an outcome not to happen: on an exchange you become the bookmaker for that selection. Pair a back bet at a bookmaker with a lay on the exchange and you cover both results, which is the whole basis of matched betting. This lay bet calculator on ToolsGambling returns the exact lay stake, the liability the exchange will hold, and your profit whichever side wins, for normal qualifiers and for both types of free bet. It handles commission, underlay and overlay, and decimal, American or fractional odds. Everything here is free, with no account and no paywall on the numbers.
What is a lay bet?
When you back a selection you bet on it to win. When you lay it, you bet on it to lose, and you take on the role the bookmaker usually plays. If the selection loses you keep the backer's stake minus commission; if it wins you pay the liability, which is the lay stake times (lay odds minus one). Matched bettors lay the same selection they backed at a bookmaker so the two positions cancel out. Get the lay stake right and you either lock a small, known qualifying loss or, with a free bet, a guaranteed profit.
The number that trips people up is liability, not the lay stake. The exchange ring-fences the full liability the moment you place the lay, so a $10 back at long odds can tie up $60 or more on the exchange. I learned early to keep enough in the exchange balance for the liability, not just the lay stake, and to double-check the commission field before I click. Get those two right and matched betting is genuinely low-variance.
Why bettors lay
The main reason is matched betting: turning bookmaker free bets and promos into real, near-guaranteed money by covering the other side on an exchange. A qualifying bet costs a few cents to unlock a free bet, then the free bet is layed for a profit of roughly 70 to 95 percent of its face value. Layers also use the exchange to trade prices, to hedge a bet that moved, or simply to bet against a selection they think will lose. The exchange gives you the one thing a bookmaker never will: the ability to be on the other side.
Why this lay bet calculator is different
Most lay calculators do one job: a normal qualifier. This one goes further, because free bets and weighting are where the real matched-betting value lives. Here is what ToolsGambling adds that the others leave out.
Qualifier, SNR and SR in one place
A normal qualifier, a stake-not-returned free bet, and a stake-returned free bet each use a different lay formula. This tool switches the math with the bet type and shows the extraction rate, so you always lay the right amount. Rivals often cover only the qualifier.
Underlay and overlay weighting
Equalising is not the only option. Underlay lays a little less so you profit more if the back wins; overlay lays more so you profit more if the lay wins. Almost no free calculator gives you this dial, which matters for in-play and value plays.
Commission presets and any rate
One tap sets Betfair 5%, Smarkets 2% or Betdaq 2%, or type your own discounted rate. Commission sits in the lay-stake formula, so the tool keeps the lock exact instead of leaving you a few cents out.
Liability shown, not hidden
The calculator puts liability next to the lay stake, because that is the amount your exchange actually holds. Beginners who watch only the lay stake run out of exchange balance; this keeps the real number in front of you.
Free, shareable and embeddable
Every number is free with no signup. Share a scenario as a link that reopens with your exact inputs, or drop the widget into your own blog with one line of code. Competitors gate this behind accounts or paid memberships.
How to use the lay bet calculator on ToolsGambling
Choose the bet type: qualifier for a normal bet, SNR or SR for a free bet. Enter your back stake, your back odds and the lay odds from the exchange, then set the commission or tap an exchange preset. Read the lay stake to place and the liability the exchange will hold, plus the profit if the back wins and if the lay wins. For a free bet the tool shows the guaranteed profit and the extraction rate. It is all free on ToolsGambling.com, with no signup.
Qualifier vs SNR vs SR free bets
A qualifier is a normal real-money bet, and because you pay the bookmaker margin on one side and commission on the other, it settles at a small known loss you accept to unlock an offer. An SNR free bet returns only the winnings, not the stake, so its lay formula drops the stake and it extracts roughly 70 to 80 percent of face value. An SR free bet returns the stake as well, so the whole payout is yours and it extracts around 90 to 95 percent, but SR offers are far rarer. Pick the right type in the tool and the lay stake and profit adjust automatically.
Equalise, underlay or overlay
A normal lay equalises both outcomes for the same profit whichever wins, which is what most matched betting wants. Underlay lays a smaller stake, so you keep more if your selection actually wins, useful when you back something you expect to come in or when you plan to leave the bet partly in play. Overlay lays a larger stake, weighting the profit to the lay side. All three respect the same commission and bet type, so you can see the exact floor and ceiling before you stake.
How exchange commission works
Exchanges do not build a margin into their odds like bookmakers; they charge a commission on your net winnings instead. Betfair is 5 percent as standard, though loyalty discounts can lower it, while Smarkets and Betdaq sit at 2 percent. Commission lives in the denominator of the lay-stake formula, so a higher rate means a slightly larger lay stake and a slightly smaller lock. Always match the commission field to your exchange, or the numbers will drift.
Lay betting vs back betting, arbitrage and dutching
Backing bets on a selection to win; laying bets on it to lose. Matched betting pairs the two to cancel risk and bank promo value. Arbitrage backs every outcome across different books so a profit is locked with no promo needed, while dutching backs several selections on the same side for an equal return. Hedging lays or backs the opposite of a bet you already hold to lock a result after the odds moved. They overlap, but the lay is the exchange tool that makes matched betting and most hedges possible. Our matched betting, arbitrage, dutching and hedge calculators cover the rest.
The honest truth about matched betting
Matched betting is low-risk, not no-risk, and it is not free money without care. A mistake, a price that moves before your lay matches, or a fat-finger stake can cost real money, and the qualifying loss is a genuine loss you only recoup from the free bet. Bookmakers also limit or close accounts that clear offers aggressively. Done carefully, with the right lay stake and enough exchange balance for the liability, it is one of the few genuinely positive-expectation edges a recreational bettor can access, but it rewards discipline over greed.
Common lay betting mistakes
The first is funding only the lay stake and not the liability, then being unable to place the lay. The second is forgetting commission, or using the wrong exchange rate, which leaves the lock a few cents out. The third is laying an SNR free bet with the qualifier formula, which over-lays and cuts your profit. The fourth is chasing very long odds for a higher extraction rate while ignoring the huge liability it demands. Match the bet type, fund the liability, and check the commission before every lay.
Lay betting terms
- Lay bet
- A bet that a selection will NOT happen, placed on an exchange where you act as the bookmaker.
- Liability
- What you pay out if the lay loses, equal to lay stake times (lay odds minus one). The exchange holds it until settlement.
- Matched betting
- Pairing a back bet at a bookmaker with a lay on an exchange to extract guaranteed value from free bets and promos.
- SNR free bet
- Stake Not Returned: a free bet that pays only the winnings, not the stake. Extracts about 70 to 80 percent of face value.
- SR free bet
- Stake Returned: a free bet that pays the stake back too, so the whole payout is yours. Extracts about 90 to 95 percent.
- Qualifying loss
- The small, known loss on a real-money qualifier, accepted to unlock a free bet worth far more.
- Commission
- The exchange's fee on net winnings, typically 2 to 5 percent. It sits in the lay-stake formula and shaves the lock.
Free betting tools on ToolsGambling.com
On ToolsGambling.com the lay bet calculator is free, like every tool here. Pair it with these to run the full matched-betting and value workflow.
Bet responsibly
Matched betting is low-risk only with discipline, on money you can afford to lose, not your rent. Set limits, never chase losses, and if betting stops being fun, get free, confidential help at BeGambleAware.org.
Evgeniy Volkov
Verified ExpertFullstack developer with a background in mathematics. I build the calculators and game-style tools on ToolsGambling with Pixi.js and modern web tech, and every result uses transparent probability formulas you can verify yourself.