Back at the bookmaker, lay on the exchange, and the outcome no longer matters. This works out the lay stake that levels both sides, the liability you need available, and the qualifying loss or locked-in profit.
Matched betting turns bookmaker offers into near-guaranteed profit by covering both outcomes. You back a selection with the bookmaker and lay the same selection on an exchange, so whatever happens the two bets cancel out. The calculator works out the exact lay stake that levels both sides, the liability you need available, and the qualifying loss or locked-in profit.
A typical offer runs in two steps. First a qualifying bet with your own money unlocks a free bet, accepting a tiny loss of pennies. Then the free bet itself: because the stake is not returned, you lay a little less than the level-profit stake and keep roughly 70–80% of the free-bet value as guaranteed profit, whichever way it lands.
The whole thing lives or dies on the numbers, so the lay stake and liability must be precise. Switch the mode to handle a normal qualifying bet or a stake-not-returned free bet, and the calculator adjusts the maths accordingly.