Free Bet Calculator
Calculate the lay stake, liability and locked-in result for bookmaker free bets. Covers qualifying bets, stake-not-returned (SNR) and stake-returned (SR) free bets, with your exchange’s commission built in, so the result is the same whichever side wins.
Use this mode for qualifying bets: the real-money bets you place to unlock a free bet. The aim is a small, known qualifying loss, usually a few percent of the stake when the back and lay odds are close.
Decimal or fractional
Decimal, as shown on the exchange
| If the selection | Bookmaker | Exchange | Net |
|---|---|---|---|
| Wins | |||
| Loses |
The result holds only if both bets are matched at these exact odds. Check the exchange has enough money available at your lay price before you place the back bet.
The lay stake formula
Divide what the back bet pays by the lay odds minus the commission (as a decimal, so 2% is 0.02). That sets a lay stake that leaves the same result whichever side wins.
Lay stake = back stake × back odds ÷ (lay odds − commission)Lay stake = free bet × (back odds − 1) ÷ (lay odds − commission)Worked example
A £25 SNR free bet backed at 5.0 and laid at 5.2 with 2% commission needs a lay stake of £25 × 4 ÷ 5.18 = £19.31, with £81.08 liability. Either way the result is £18.92, keeping 75.7% of the free bet as cash.
Best Free Bet Offers
Claim a welcome offer, then use the calculator above to work out the lay stakes. UKGC-licensed bookmakers only. 18+. T&Cs apply.
18+ New customers only. Bet £10+ at odds Evens (2.00)+. Get 4 × £10 free bets. 7-day expiry. T&Cs apply. BeGambleAware.org
18+ New UK customers only. Bet £10+ at Evens (2.00)+. Get 50% back of first day losses as a free bet up to £25. Valid 7 days. Min. 3 bets required. T&Cs apply. BeGambleAware.org
18+ New customers only. Promo code BET40GET20. Place a £40+ real cash first bet at odds of Evens (2.0)+ to get 2 × £10 free bets: the second is paid 24 hours after the first. Free bets must be used at odds of 4/1 (5.0)+, cannot be split and expire after 24 hours. Void and cashed-out bets do not qualify. T&Cs apply. BeGambleAware.org
18+ New players only. Code: NEW30. Bet & settle 1 × £10 on Exchange (odds 2.0+) & 1 × £10 Bet Builder/Multiple (odds 3.0+, min 3 selections). 3 × £10 free bets credited within 72hrs. T&Cs apply. BeGambleAware.org
18+ New customers only. Place & settle £20 on easyBet markets across at least 2 different events at odds 2.0+. Skrill/Neteller/PaySafe excluded. T&Cs apply. BeGambleAware.org
18+ New customers only. Min deposit £20. Bet £10+ at odds 2.0+ to receive 3 × £5 free bets. T&Cs apply. BeGambleAware.org
All bookmakers listed hold a UK Gambling Commission licence. New customers only. 18+. Offers change often, so check the terms on the bookmaker’s site before you bet.
Related Betting Tools
How to Use the Free Bet Calculator
The calculator takes the guesswork out of matched betting by working out the exact lay stake to place on a betting exchange. Whether you are placing a qualifying bet to unlock a welcome offer or turning a free bet into cash, it shows what to stake, your liability and your result for every outcome.
- Choose the bet type.Qualifying bet for the real-money bet that unlocks an offer. Free bet (SNR) for the usual kind of free bet, where only the winnings are paid. Free bet (SR) for the rarer kind that pays the stake back too.
- Enter the back bet.Your stake (or the free bet’s value) and the bookmaker’s odds. For qualifying bets, look for a selection where the back and lay odds are close. For SNR free bets, higher odds (around 4.0 and up) keep more of the free bet.
- Enter the lay bet.The lay odds on your betting exchange and its commission rate. Smarkets’ standard rate is 2% and Betfair’s is 5%, but check your own account, because rates vary.
- Read your results.The panel shows the lay stake, the liability you need at the exchange, and your result if the selection wins or loses. For free bets, the bar shows how much of the face value you keep.
Matched Betting Formulas
Knowing the maths behind the calculator helps you check results and spot mistakes. In each formula, commission is written as a decimal, so 2% is 0.02.
Lay stake = (back stake × back odds) ÷ (lay odds − commission)Lay stake = (free bet × (back odds − 1)) ÷ (lay odds − commission)Lay stake = (free bet × back odds) ÷ (lay odds − commission)Liability = lay stake × (lay odds − 1)These formulas make the result identical whichever way the selection goes. A £10 qualifying bet at 3.0, laid at 3.1 with 2% commission, needs a lay stake of £30 ÷ 3.08 = £9.74 and leaves a qualifying loss of £0.45 either way.
Understanding Free Bet Types
What is an SNR free bet?
SNR stands for stake not returned. It is the most common type of free bet from UK bookmakers. If your SNR free bet wins, you get the winnings but not the stake. A £25 SNR free bet at odds of 5.0 pays £100 if it wins, without the £25 stake. A well-matched SNR free bet usually keeps around 70% to 80% of its face value.
What is an SR free bet?
SR stands for stake returned. These are rarer and worth more: if an SR free bet wins, you get the winnings and the stake. A £25 SR free bet at 5.0 returns £125 (£100 winnings + £25 stake). It is laid with the same formula as a qualifying bet, except that a losing back bet costs you nothing.
What is a qualifying bet?
A qualifying bet is the first real-money bet you place with a bookmaker to unlock its free bet offer. Most welcome offers follow a “bet X, get Y” format, so the free bet arrives only after the qualifying bet. The aim in matched betting is to keep the loss on that bet small, often a few percent of the stake when the odds are close. If the qualifying bet has to be an acca, use our accumulator calculator to work out the combined odds.
Tips for Getting the Most From a Free Bet
Close the odds gap on qualifying bets
The closer the back and lay odds, the smaller your qualifying loss. Look for selections where the bookmaker and exchange prices are within 0.1 or 0.2 of each other. Football match odds and popular horse races tend to give the closest matches.
Use higher odds for SNR free bets
Higher odds keep more of an SNR free bet. With the lay odds equal to the back odds and 2% commission, a free bet at 3.0 keeps about 65.8% of its value, at 5.0 about 78.7%, and at 8.0 about 86.0%. A gap between back and lay odds trims these figures. If your free bet can be used each way, see our each way calculator and our guide to each way markets.
Check exchange liquidity
Before you place the back bet, check there is enough money on the exchange at your lay odds. If less is available than your lay stake, the rest may be matched at worse odds, or not at all, and the locked-in result no longer holds.
Know the other risks
Matched betting removes the risk of the result, not every risk. Odds can move between placing the two bets, a bet can be placed at the wrong stake, and bookmakers can restrict accounts that only take offers. Free bets also come with terms, such as minimum odds and expiry dates, that you need to meet.
Keep records
Record every qualifying bet, free bet and result. Gambling winnings are not taxed in the UK, but good records show what you have really made and which offers are worth your time.
Frequently Asked Questions
What is a free bet calculator?
A free bet calculator works out the lay stake to place on a betting exchange when you use a bookmaker free bet or promotion. It sets the lay stake so the result is the same whether your selection wins or loses: a small loss on a qualifying bet, or a locked-in profit on a free bet. It is the main tool for matched betting on welcome offers.
What is the difference between SNR and SR free bets?
SNR (stake not returned) free bets pay only the winnings if they win, without the stake. SR (stake returned) free bets pay the winnings and the stake. SR free bets are worth more but much rarer: most UK welcome offers give SNR free bets.
Is matched betting legal in the UK?
Yes, matched betting is legal in the UK. It uses bookmaker promotions and a betting exchange so that both outcomes are covered and the result does not depend on who wins, provided both bets are matched at the prices you calculated. Gambling winnings, including matched betting profits, are not taxed in the UK. Bookmakers can restrict accounts that only use offers.
How much can I make from a free bet?
A typical SNR free bet, matched well, keeps around 70% to 80% of its face value. So a £25 free bet usually locks in roughly £17.50 to £20. The exact figure depends on the odds you use, the gap between back and lay odds, and your exchange commission.
What exchange commission should I use?
Use the rate on your own exchange account. Smarkets’ standard rate is 2% and Betfair’s standard rate is 5%, but rates vary with promotions and account type, so check before you calculate. Lower commission means a better result.
What odds should I use for free bets?
For qualifying bets, use the closest back and lay odds you can find, ideally within 0.1 or 0.2 of each other. For SNR free bets, higher odds, roughly 4.0 to 6.0, keep more of the free bet. Above about 8.0 the gain is small and exchange liquidity can be thin. For SR free bets, the odds matter less because the stake comes back.
Why do my win and lose results come out the same?
That is the point of the calculation. The lay stake is set so the net result is identical whichever way the selection goes: the bookmaker bet and the exchange bet cancel out apart from the small qualifying loss or the free bet profit. If your figures differ, the lay was not matched at the odds you entered.
Learn More About Betting
Compare the latest welcome offers in our best betting sites guide, or read our bookmaker reviews for detailed analysis of each operator’s odds, markets and withdrawal times.
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