Bonus Buy Calculator

A bonus buy calculator puts real numbers on the “just one more buy” feeling. Bring £500, buy bonuses at 100× a £1 bet on a high-volatility slot with 96.5% RTP, and plan 20 buys. In 10,000 simulated sessions the money ran out before buy 20 in 65% of them. Only 22% of individual bonuses paid back their £100 price, and a typical session ended with about £84 left. The free calculator above runs your own numbers.

How the bonus buy calculator works

Every bonus result is drawn from a long-tailed spread of payouts, set so the average is exactly the RTP you enter and nothing pays more than the max win. Most buys return less than they cost. A few return many times more. That’s what high volatility means, and it’s why bonus buys feel brutal on a small bankroll.

Some numbers are plain arithmetic:

Cost per buy = bet × price multiple
Average loss per buy = cost × (1 − RTP)
Buys you can afford outright = bankroll ÷ cost

At 96.5% RTP, a £100 buy costs you £3.50 on average. That’s small. The problem is the spread around it. You need roughly 100 buys before your result starts to look like the average.

Things worth knowing before you buy

• Check the bonus buy RTP. Some games pay a slightly different RTP on bought bonuses than on spins. It’s in the game rules.
• Volatility changes everything. Switch from high to low and the bust chance in the example falls from 65% to about 21%, even though the average loss per buy is identical.
• Bankroll in buys, not pounds. Five buys of headroom is very little. If you want a decent chance of seeing 20 bonuses, you need far more than 20 × the price.

Spinning instead of buying? The slot bankroll calculator covers spins, and the slot simulator lets you watch a session play out.

Collecting bonuses to open later instead? The bonus hunt tracker works out the break-even multiplier as you go.

Play for fun with money you won’t miss. If you’re spending more than you planned, BeGambleAware.org is free and confidential.