WhichBookmakerCalculator · 2026-09-24
Free bet calculator
Enter the free bet and the odds you would use it at. You get the cash if it wins, the average value across many bets, and the odds that make the most of it — with the bookmaker's margin included, which is the part most calculators leave out.
18+. Real prices carry a margin, so the true chance is lower than 1 ÷ o. We divide the fair probability by (1 + margin) to allow for it. A 5% margin turns a £10 free bet at 3.0 from £6.67 into about £6.35.
The same free bet at different odds
Why the odds matter more than the amount: the stake is not returned, so the value rises with the price. This is your free bet at each price, margin included.
| Odds | Collect if it wins | Worth on average | Share of face value |
|---|---|---|---|
| 1.5 | |||
| 2.0 | |||
| 2.5 | |||
| 3.0 | |||
| 4.0 | |||
| 5.0 | |||
| 8.0 |
How the calculator works
A standard free bet returns the winnings but not the stake. At decimal odds o, a free bet of F pays F × (o − 1) if it wins and nothing if it loses.
The average value is that payout multiplied by the chance of winning. In a fair market the chance is 1 ÷ o, so the value is F × (1 − 1 ÷ o). At 2.0 that is half the face value; at 3.0 two thirds; at 5.0 four fifths.
Real prices carry a margin, so the true chance is lower than 1 ÷ o. We divide the fair probability by (1 + margin) to allow for it. A 5% margin turns a £10 free bet at 3.0 from £6.67 into about £6.35.
Getting the most from a free bet
- Use it at longer odds than you would with your own money. The stake is lost either way, so only the profit counts.
- Split a large credit into two or three bets around 3.0 to 5.0 rather than one long shot: the same average value with less variance.
- Check the minimum odds in the offer terms. Many require at least 1.5 or 2.0 on the qualifying bet and on the free bet itself.
- Watch the expiry. Free bets typically lapse after 7 to 30 days, and unused credit is the bookmaker's cheapest outcome.
Link to this calculator
Free to link, quote or embed. If you use the numbers in an article or a forum post, a link back is all we ask.
https://whichbookmaker.io/in/free-bet-calculator<a href="https://whichbookmaker.io/in/free-bet-calculator">Free bet calculator — WhichBookmaker</a>Text and method: CC BY 4.0. Attribute to WhichBookmaker with a link.
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Frequently asked questions
How much is a £10 free bet worth?
It depends on the odds you use it at. In a fair market a £10 free bet is worth £5 at 2.0, £6.67 at 3.0 and £8 at 5.0, because the stake is not returned and only the profit counts. Allow for a typical 5% margin and those figures fall to roughly £4.76, £6.35 and £7.62.
Why is a free bet not worth its face value?
Because the stake is not returned with the winnings. Bet £10 of your own money at 2.0 and you collect £20; bet a £10 free bet at 2.0 and you collect £10. The face value is only ever reached if the odds are extremely long, and by then the chance of winning is very small.
What odds should I use a free bet at?
Longer than you would with cash, but not so long that it almost never wins. Around 3.0 to 5.0 keeps 65% to 80% of the face value on average and still wins often enough to matter. Splitting the credit across two or three selections in that range smooths the variance.
Does the calculator include the bookmaker's margin?
Yes. Most free bet calculators assume a fair market, which flatters every result. We divide the fair probability by one plus the margin you enter; 5% is a reasonable default for a main football market, and you can set it to 0 to see the fair-market figure.