A slot bankroll calculator answers the question RTP alone can’t: how long will £200 actually last? Two slots can share a 96% RTP and still behave completely differently, because one pays little and often and the other saves it all for rare big hits. Put in your bankroll, bet size, RTP and the game’s volatility, and the free calculator above estimates how many spins you get and how likely the money is to run out first.
The starting example is £200 at £1 a spin on a 96% medium volatility slot, planning 1,000 spins. The chance of going bust before the end is about 36%.
Slot bankroll calculator: two numbers to watch
Average spins before the money’s gone. On a 96% game you lose 4p of every £1 bet on average. £200 ÷ 4p = 5,000 spins, or about ten hours at 500 spins an hour. That’s the long-run average, and it depends only on RTP and bet size.
The chance of running out within your session. This is where volatility comes in. You’ll lose about £40 over 1,000 spins on average, but the typical swing either way is closer to £190. Some sessions end well up. A lot end with the bankroll gone well before spin 1,000.
What changes the risk most
Same £200, same 1,000 spins, changing one thing at a time:
| Change | Chance of going bust |
|---|---|
| Starting point: £1 spins, 96% RTP, medium volatility | 36% |
| Bet 50p instead of £1 | 5% |
| Bet £2 instead of £1 | 66% |
| Low volatility slot | 8% |
| High volatility slot | 57% |
| Very high volatility slot | 70% |
| 94% RTP instead of 96% | 40% |
| 97% RTP instead of 96% | 34% |
The surprise for most people is the bottom two rows. Over a single session, a couple of points of RTP barely moves the risk. Bet size and volatility move it a lot. RTP decides how fast you lose over months, while volatility decides how bumpy tonight is.
How the estimate works
The calculator treats a session as a random walk. Each spin loses the house edge on average, with a spread set by the volatility: a standard deviation of about 3 bets per spin for low volatility, 6 for medium, 10 for high and 15 for very high. If a game publishes its own figure, put it in under “More options”. Real slots are lopsided, with lots of small losses and the odd big win, so we checked the formula against simulations of slots shaped like that. It comes out slightly cautious, a few points higher than the simulations.
To find the RTP and house edge of a game, use the RTP calculator. Playing through a bonus? The wagering requirement calculator works out how much you’ll need to bet, and the free spins value calculator shows what an offer is worth.
Set the bankroll as money you’re fine losing, and stop when it’s gone. BeGambleAware.org is free and confidential if it stops being fun.