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Calculate lay bet liability and profit on betting exchanges. Includes matched betting optimizer for qualifying bets and free bet (SNR) conversions.
| Outcome | P&L | ROI on liability |
|---|---|---|
| Selection loses (lay wins) | +$98.00 | +49.0% |
| Selection wins (lay loses) | в€’$200.00 | в€’100% |
| Outcome | P&L |
|---|---|
| Back wins (bookie pays, you pay exchange) | $-4.55 |
| Lay wins (exchange pays, bookie keeps stake) | $-4.55 |
Lay betting means betting against an outcome — you act as the bookmaker. On exchanges like Betfair, Smarkets, or Matchbook, you lay a selection and another user backs it. If the selection loses, you collect their stake (minus commission). If it wins, you pay their winnings — your liability = backer stake × (lay odds − 1).
Lower lay odds mean lower liability relative to potential profit. Laying a 1.20 favourite risks £2 liability per £10 backer stake. Laying a 5.00 outsider risks £40. This is why professional lay bettors focus on favourites — limited downside, consistent small profits.
Matched betting combines a back bet at a bookmaker with a lay bet on an exchange to cover both outcomes simultaneously. This lets you extract free bets and promotions with near-zero risk. For a qualifying bet, you accept a small calculated loss to unlock a free bet. For the free bet (SNR), you lay it off and convert 60–85% to guaranteed cash.
The conversion rate of an SNR free bet depends primarily on the back odds and lay odds. Higher back odds = higher conversion rate. An £100 free bet at 5.00 back / 5.10 lay with 2% commission returns approximately £77 — 77% conversion. At 3.00 / 3.10, the conversion drops to around 60%.
LAY BET
Liability = Backer Stake Г— (Lay Odds в€’ 1)
Profit = Backer Stake Г— (1 в€’ Commission%)
Example: Lay ВЈ100 at 3.00 / 2% commission
Liability = ВЈ100 Г— 2.00 = ВЈ200
Profit = ВЈ100 Г— 0.98 = ВЈ98
MATCHED — Qualifying bet (real money back)
Lay Stake = (Back Stake Г— Back Odds) / (Lay Odds в€’ Commission%)
Example: ВЈ100 back @3.00, lay @3.10, 2% comm
Lay Stake = (100 Г— 3.00) / (3.10 в€’ 0.02) = ВЈ97.40
Qualifying loss ≈ −£4.54 each side ✓
MATCHED — SNR Free Bet
Lay Stake = Back Stake Г— (Back Odds в€’ 1) / (Lay Odds в€’ Commission%)
Example: ВЈ100 SNR free bet, back @5.00, lay @5.10, 2% comm
Lay Stake = 100 Г— 4.00 / (5.10 в€’ 0.02) = ВЈ78.74
Guaranteed profit ≈ +£77 (77% conversion) ✓A back bet is a traditional bet that something will happen. A lay bet is the opposite — you bet that something will NOT happen, acting as the bookmaker. Lay betting is only possible on betting exchanges like Betfair, Smarkets, or Matchbook, where you are matched against another bettor wanting to back.
Commission is charged on your net winnings — not stakes. If you win £100 with 2% commission, you keep £98. Standard rates: Betfair 2% (Premium Charge applies to highly profitable accounts), Smarkets 1%, Matchbook 1.5–2%. Enter your exact rate in the calculator for accurate results.
A qualifying bet is the initial real-money bet you place to unlock a bookmaker's free bet offer — e.g., 'Bet £10 get £10 free'. You back with the bookmaker and lay on the exchange, accepting a small qualifying loss (typically £0.50–£2) to receive the free bet, which you then convert to ~60–85% guaranteed cash.
SNR = Stake Not Returned. If your selection wins, you receive only the winnings, not your original stake. This is the most common free bet type. The lay stake differs from qualifying bets: Lay Stake = Free Bet Г— (Back Odds в€’ 1) / (Lay Odds в€’ Commission%). SR (Stake Returned) free bets are calculated like qualifying bets.
Yes. Matched betting is legal in the UK, Ireland, and most countries. It exploits bookmaker promotions using mathematical arbitrage between a bookmaker and exchange. Bookmakers may limit accounts of consistent matched bettors over time, but the practice is legal and not traditional gambling — both outcomes are covered.