What is a free bet?
Free bet: A free bet is a token issued by a bookmaker that you can stake on a market without using your own money: the engine of matched betting.
A free bet is a token a bookmaker issues you, usually after you've placed a qualifying bet, that lets you stake on a market without using any of your own money. It appears in your account as a credit you select on the bet slip (£30 at Bet365, £20 at Sky Bet), and once it's placed it behaves like an ordinary bet, except that the stake itself isn't yours to lose.
Free bets are the engine of matched betting. Almost every welcome offer in the UK is structured as "stake £X of your own money, get £Y in free bets". The free bet is where the extracted value sits. Sized correctly with our standard calculator and laid off at an exchange, a free bet's value to a matched bettor is typically 70–85% of its face value. A £30 free bet, in other words, is worth around £21–£25 in real cash once you've worked it through. The mechanics are walked through end-to-end in our free bets guide and from scratch in our matched betting beginner guide.
Two details matter when you're sizing a free bet. First, the free-bet variant: most UK free bets are stake-not-returned, where the bookmaker keeps the stake and pays out only the winnings; a smaller number are stake-returned and pay out the stake too. SNR extracts about 75–80% of face; SR extracts close to 95%. Second, the odds: free bets work best at higher odds, typically in the 5.0–10.0 range, because that's where laying off captures the most of the face value. The calculator shows the projected extraction for any back-lay pairing, so you can choose markets accordingly.
Worked example
Bet365 credit a £30 SNR free bet to your account after the qualifying bet has settled. You back £30 on a 6.0-priced selection at Bet365 (free-bet stake) and lay £19.40 at 6.10 on Smarkets. If the back wins, the bookmaker pays out £150 winnings (no stake returned because it's SNR), the exchange takes £99.45 of liability, and you net around £24. If it loses, the lay leg pays you £19.40 (less commission), and you net around £19. The variance between the two outcomes is small enough that the free bet's expected extraction is about £22, roughly 73% of face.
That's the matched-betting use of a free bet. A casual punter who simply stakes the £30 on a coin-flip favourite and walks away typically extracts much less, because they're not capturing the free-bet value across both possible outcomes.
Common mistake
Confusing a free bet with a bonus bet. Both arrive in your account as credit, but a bonus bet usually has wagering requirements attached. A £30 bonus bet with 3× wagering means £90 of bets before any cash converts. A real free bet has no wagering attached: place it, lay it off, take the value. Always check the offer T&Cs for "wagering", "rollover", or "playthrough" before treating any credit as a free bet.