Most gambling calculators answer the question "what could I win". This one answers the question the maths can actually answer: given a bankroll, a stake and a published return figure, roughly how much play does that money buy before it is expected to be gone.
The arithmetic
house edge = 1 − RTP
cost per spin = stake × house edge
spins bankroll buys = bankroll ÷ cost per spin
total staked = bankroll ÷ house edge
cost per hour = stake × spins per hour × house edge
Check the default on paper. At 96% RTP the edge is 4%. A 50p spin costs 2p on average. £100 divided by 2p is 5,000 spins. Those 5,000 spins at 50p put £2,500 through the game — twenty-five times the money you brought — and at 500 spins an hour they take ten hours, at £10 an hour.
That £2,500 figure is the one worth sitting with. The house edge is not charged on your deposit. It is charged on turnover, and the same £100 is staked, partially returned, and staked again until it has been through the game twenty-five times over. This is why "I only lost £100" and "the game took £2,500 in stakes" describe the same evening, and why a small change in the return figure moves the total by a lot.
Speed is the input that matters most
Two settings, same game, same money:
| Stake | Spins/hour | RTP | Cost per hour | £100 lasts |
|---|---|---|---|---|
| £0.20 | 300 | 96% | £2.40 | about 42 hrs |
| £0.20 | 600 | 96% | £4.80 | about 21 hrs |
| £0.50 | 500 | 96% | £10.00 | about 10 hrs |
| £0.50 | 500 | 92% | £20.00 | about 5 hrs |
| £2.00 | 500 | 96% | £40.00 | about 2.5 hrs |
Halving the return figure from 96% to 92% doubles the cost. So does doubling the stake, and so does doubling the speed. Players spend a lot of attention on the first of those and almost none on the other two, which is backwards: RTP is fixed by the game, while stake and speed are the only two variables in the whole product that you actually control.
Reading the RTP figure correctly
Take it from the game's own information screen rather than from a general figure. The same slot title is frequently supplied to operators at more than one return setting, so a game you know well can be a materially different proposition under an identical name and theme elsewhere. Feature buys, where offered, often carry their own return figure that differs from the base game.
And note what the figure is measured over. Published RTP is calculated across an enormous number of simulated spins, because that is the only sample in which it means anything. A few hundred spins on a high-volatility game will usually come nowhere near it — the median session is worse than the average, because the average is held up by rare outcomes most sessions never reach. The number above is a price, not a prediction.
Using it as a budget
The most useful way to read the output is backwards. Decide what an evening is worth to you — the way you would price a cinema ticket or a round of drinks — then find the stake and speed that produce that figure, and set a deposit limit at it before you start. £5 an hour is 20p spins at 600 an hour on a 96% game. £40 an hour is the same game at £2.
Setting the limit is the part with teeth, and the asymmetry described on the player protection page is what makes it work: reductions apply immediately, increases are held.
18+. This tool prices play; it does not improve the odds, and no staking pattern changes the house edge. Free confidential support: 0808 8020 133 or BeGambleAware.