Betting maths on the numbers you enter. Amounts are in pounds (£).
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Free bet calculator
Bookmaker (back)
£
Exchange (lay)
%
Exchanges charge commission on lay winnings. Enter your exchange's rate.
Lay stake£7.69£7.69
Liability (needed in the exchange)£32.31£32.31
If the bookmaker bet wins
+£7.69+£7.69
If the exchange lay wins
+£7.69+£7.69
Conversion rate (of the free bet)
76.9%76.9%
How the Free Bet calculator works
What it does
A free bet from a bookmaker is only worth something if it wins. This calculator works out a lay bet at a betting exchange that balances it, so you end up with about the same amount whichever side wins.
It shows the lay stake, the liability you need at the exchange, the result either way after commission, and the conversion rate: how much of the free bet's face value you keep.
How to use it
Choose the free bet type. Most are stake not returned: a win pays the winnings but not the free bet itself.
Enter the free bet amount and the back odds you will use it at.
Enter the lay odds at the exchange, and its commission (leave it at 0 if there is none).
Check the two results match, then make sure you can cover the liability before you lay.
Worked example
Made-up numbers, for learning
A £10 free bet, stake not returned, used at 5.00. The same selection can be laid at 5.20 on an exchange charging 2% commission.
The lay stake is £7.72, and the liability is £32.43.
If the bookmaker bet wins, the result is +£7.57. If the exchange lay wins, it is also +£7.57.
That is a conversion rate of 75.7% of the free bet.
Things to watch
Offers have terms and limits, such as minimum odds, expiry dates and which markets count. Read them first.
Odds and lay availability change quickly. If the price or the amount you can lay moves, the two bets stop matching.
A lay bet needs the liability held in your exchange account, which can be several times the lay stake at longer odds.
Bookmakers may restrict accounts that use offers this way.
Exchanges charge commission on lay winnings. Enter your exchange's rate, or the results will look better than they are.
Key words
Free bet (stake not returned)
A free bet whose win pays only the winnings, not the free bet amount.
Free bet (stake returned)
A less common free bet whose win also pays back the free bet amount.
Lay bet
A bet at an exchange that a selection will not win.
Liability
What you pay out if the lay bet loses: lay stake × (lay odds − 1).
Conversion rate
The result as a share of the free bet's face value.
Results are a record of maths on the numbers you enter, not advice.
