Matched Betting Calculator

Matched betting is a UK-specific arbitrage technique that extracts the value out of bookmaker free-bet promotions. You back a result with a high-street bookie (say, Bet365) and lay the same result on a betting exchange (Betfair, Smarkets or Betdaq), so the two bets cancel each other out. With a qualifying bet you usually lose a small amount; with a free bet you keep most of the bonus stake as a guaranteed return.

It is not a betting system, a tipping service or a way to beat the bookies at sports prediction. The maths is fixed and the profit is locked in before the match kicks off. The catch is that bookmakers spot pattern-matching customers within weeks, so accounts get gubbed (limited or closed). Most people make a few thousand pounds during the welcome-offer phase, then the well runs dry.

The calculator has three modes because free bets are not all created equal. Use Normal mode for any qualifying bet placed with your own cash, this is the small loss you take to release the free bet. Use Free Bet SNR (Stake Not Returned) for the most common type of free bet, where the bookie keeps the stake and you only collect winnings if the back bet wins. Use Free Bet SR (Stake Returned) for rarer promotions where the stake is returned with any winnings, behaving more like cash.

Picking the wrong mode is the single most common matched-betting error. An SR free bet calculated as SNR will tell you to lay too little, leaving you exposed to a real loss. Always check the bookmaker's terms and conditions before placing the bet. If the offer says 'bet £10 get £30 in free bets', those are almost certainly SNR.

Lay bets on a betting exchange are not free. The exchange takes a commission on net winnings: Betfair charges 5% as standard (sometimes 2% with their loyalty discount), Smarkets charges 2% flat and Betdaq sits at 2.5%. The calculator factors this in automatically so the lay stake is correct, but it changes which exchange is the smartest choice for any given offer.

On a £20 free bet at typical odds, the difference between Betfair's 5% and Smarkets' 2% is roughly 30p of profit. That sounds trivial, but across 100 offers it adds up to £30 of pure margin lost. Most experienced matched bettors run accounts on at least two exchanges, then route each bet to whichever has the deepest liquidity at the closest available lay odds. The [odds converter](/odds-converter) and [betting odds calculator](/betting-odds-calculator) help you sense-check whether the lay price is reasonable before you click.

The lay stake on the exchange is not the cash you actually need. Your liability is the amount you would owe the exchange if the back bet wins, calculated as lay stake times (lay odds minus 1). On a £100 lay at odds of 4.0, you need £300 sitting in your exchange account. Run out of liability and the bet does not get matched, leaving the bookie side completely unhedged.

A reasonable starting bankroll for matched betting is around £200 split between bookie and exchange, which lets you cover most welcome-offer qualifying bets. Higher-odds events (long-shot horse bets, accumulator components) need significantly more float because the liability scales with the lay odds. Underestimating this is how beginners turn a guaranteed-profit hobby into a panic at the bank holiday weekend when nothing settles in time.