Promo math · 6 min read

Bonus bet conversion guide for Australian bookmakers

The practical math behind converting stake-not-returned bonus bets into cash while minimizing leakage.

What bonus bet conversion really measures

A bonus bet is not cash, so the question is how much of its face value you can turn into withdrawable money after hedging costs. Conversion rate is the share of the bonus that survives the process.

Higher back odds often increase conversion, but only if the lay side stays efficient enough to avoid blowing out liability and slippage.

The key moving parts

For a stake-not-returned bet, the back bet only returns winnings, not the original bonus stake. That changes the lay sizing formula compared with a normal qualifying bet.

Back odds determine the amount of bonus value available if the bet wins.

Lay odds determine how expensive it is to neutralize that outcome.

Exchange commission reduces what you keep when the lay wins.

Liquidity matters because the best theoretical line is useless if you cannot get matched.

Common mistakes

The biggest leakage usually comes from rushing. Many bettors take the first available market, ignore commission, or choose odds that look large without checking the lay side properly.

Forgetting that stake-not-returned math is different from standard matched betting math.

Underestimating lay liability and tying up too much working capital.

Chasing maximum conversion in a market that makes your account profile look too sharp.

How Sherwood frames promo decisions

A promo is only attractive if the EV survives both conversion friction and account-health cost. That is the broader lens Sherwood uses: a smaller immediate gain can still be the right move if it preserves a better account.