The Matched Betting Calculator handles the back/lay arithmetic used to convert sportsbook bonuses (free bets, risk-free first bets, deposit matches) into near-guaranteed profit. Place a Back bet at one sportsbook, lay the same outcome at a betting exchange (Betfair, Smarkets, Matchbook), and you collect the bonus value while exposing yourself only to a small qualifying loss.

Toggle between Back mode and Lay mode, enter the back odds, lay odds, lay commission (typically 2–5% on exchanges), and your stake — the calculator instantly returns the optimal lay stake to balance the two outcomes, the qualifying loss / underlay / overlay number, and the net profit if you're using a Free Bet (Stake Returned or Stake Not Returned). All three odds formats are supported on both the back and lay legs.

Matched betting is legal in most jurisdictions but is treated as undesirable activity by most sportsbooks — accounts are often restricted or closed once detected. Use responsibly. For arbitrage between sportsbooks (no exchange required), see the Arbitrage Calculator. For odds conversion, see the Odds Converter.