What is a matched betting calculator?
A matched betting calculator works out exactly how much to lay at an exchange to cover a back bet at a bookmaker, so you extract the value from a promotion whatever the result. It handles the two things beginners get wrong: the exchange commission and the difference between a qualifying bet and a free bet (SNR).
Switch modes at the top: Qualifying bet shows the small loss that unlocks an offer; Free bet (SNR) shows the profit you lock in from the bonus itself.
How to use the calculator
Pick the bet type
Qualifying bet or free bet (SNR).
Enter the back bet
Bookmaker odds and your stake.
Enter the lay side
Exchange odds and commission.
Read the result
Lay stake, liability and locked profit/loss.
How is matched betting calculated?
With lay commission c as a decimal (2% = 0.02):
- Qualifying bet: lay stake = (back odds × stake) ÷ (lay odds − c)
- Free bet (SNR): lay stake = ((back odds − 1) × stake) ÷ (lay odds − c)
- Liability = lay stake × (lay odds − 1)
The only difference between the two modes is the numerator: a free bet uses (back odds − 1) because a stake-not-returned bonus pays only the winnings, not the token stake.
Worked example: turning a free bet into profit
You have a €20 free bet (SNR). You back an outcome at 4.0 and lay it at 4.2 on an exchange charging 2%:
- Lay stake = ((4.0 − 1) × 20) ÷ (4.2 − 0.02) = €14.35
- Liability = 14.35 × (4.2 − 1) = €45.93
- If the back wins: 20 × 3.0 − 45.93 = €14.07
- If the lay wins: 14.35 × 0.98 = €14.07
Same profit either way — you've converted a €20 free bet into about €14 guaranteed cash (~70% retention), with no dependence on the result.
Matched betting, arbitrage or hedging?
They all use back-and-lay maths but for different goals. Matched betting extracts value from bookmaker offers; if you want a guaranteed profit from odds differences alone, that's arbitrage betting and its back lay calculator. If you already have a bet and the odds have moved, use the hedging calculator. And to read a bookmaker's price in any format, the odds converter has you covered.
Learn more about arbitrage betting
New to this? Read our full guide on what is arbitrage betting, or see the arbitrage betting formula explained step by step with worked examples. Odds in a different format? Use our odds converter to switch between decimal, fractional, American and implied probability.
Frequently asked questions
- What is matched betting?
- Matched betting is a technique that turns bookmaker free-bet and sign-up offers into (almost) risk-free cash. You back an outcome at a bookmaker and lay the same outcome at a betting exchange, so the result of the event does not decide your profit — the offer does. It is legal and relies on maths, not prediction.
- What is the difference between a qualifying bet and a free bet?
- A qualifying bet is a real-money bet you must place to unlock an offer; done right it costs only a tiny "qualifying loss". A free bet is the bonus itself — usually "stake not returned" (SNR), meaning a winning free bet pays only the profit, not the token stake. The two are calculated differently, which is why this tool has both modes.
- How do I calculate the lay stake for a free bet?
- For a stake-not-returned free bet: lay stake = ((back odds - 1) x free bet stake) / (lay odds - commission). Because the free stake is not returned, the back return is (odds - 1) x stake rather than odds x stake.
- How much of a free bet can I keep?
- With SNR free bets you typically keep 70-80% of the face value as profit, depending on the back and lay odds. Higher odds retain more. The calculator shows the exact retention percentage for the odds you enter.
- What is a qualifying loss?
- It is the small, expected loss on the real-money bet you place to trigger an offer — usually a few percent of your stake. It is not a mistake; it is the cost of unlocking a much larger free bet, which more than covers it.
- Is matched betting the same as arbitrage?
- They share the same back-and-lay mechanics, but the goal differs. Arbitrage seeks a guaranteed profit from odds differences alone; matched betting extracts value from bookmaker promotions. Matched betting usually accepts a tiny qualifying loss precisely because the free bet that follows is worth far more.