RTP calculator: the average cost of a slot, and a rough range
Enter a game's return to player, your stake and how long you play. The calculator shows what the house edge costs on average, what comes back, and how far one session might stray from that average.
Count the play by
Volatility, for the range
500 rounds in total.
The range is expected return ± 2 standard deviations, an approximation: real slot results are lopsided.
How the RTP calculator works
Return to player is the share of all stakes a game pays back over the long run, so everything else follows from one multiplication. The total staked is the stake per round times the number of rounds. The expected return is the total staked times the RTP, and the expected cost is the rest: the total staked times the house edge, which is 100% minus the RTP.
The default answer above is worked out that way: 500 rounds at £1 is £500.00 staked, and at 96% RTP the game returns £480.00 on average, so the average cost is £20.00. The figure counts every stake, including winnings played back into the game, which is why it is often larger than people expect. Someone who arrives with £50 and plays 500 rounds of £1 has staked ten times what they brought.
Switch to "Hours of play" to enter a pace instead. The calculator multiplies rounds an hour by hours to get the number of rounds, then shows the cost per hour as well as the total.
Worked examples: RTP and pace
The same session costs very different amounts depending on the game's RTP. Here are 500 rounds at £1 on a slot at each end of the usual UK range and in the middle:
| RTP | House edge | Expected return | Average cost |
|---|---|---|---|
| 94% | 6% | £470.00 | £30.00 |
| 96% | 4% | £480.00 | £20.00 |
| 97% | 3% | £485.00 | £15.00 |
A 94% game costs twice as much as a 97% one over the same stakes. Pace matters just as much. Online slots in Great Britain must take at least 2.5 seconds per round, which puts a ceiling of 1,440 rounds on an hour. At £1 a round and 96% RTP, the average cost of an hour looks like this:
| Rounds an hour | Seconds a round | Average cost of the hour |
|---|---|---|
| 300 | 12.0 | £12.00 |
| 600 | 6.0 | £24.00 |
| 1,440 | 2.5 | £57.60 |
Pauses, bonus rounds and reading the screen all slow real play down, so timing yourself for a few minutes gives a better figure than the maximum. The point stands, though: halving the pace halves the cost per hour, just as a game with twice the house edge costs twice as much.
The range, and why it is only a rough guide
The average cost is exact; what happens in one session is not. To give a sense of the spread, the calculator adds a range: the expected return plus or minus two standard deviations of the session total. The standard deviation of a session grows with the square root of the number of rounds: stake × σ × √rounds, where σ is the standard deviation of one round's return, in stakes.
Games do not publish σ, so the calculator offers three levels we defined for illustration: low (3 stakes), medium (7) and high (15). They are round numbers chosen to bracket gentle and very swingy games, not measurements of any particular title. For scale, the fully worked example slot on our slot machine odds page, whose every result is known, comes out at 6.54, close to the medium level.
The range is honest about the size of the swings but not about their shape. A normal approximation assumes results are symmetrical around the average, and slot results are not: most rounds lose, a few pay a lot, so sessions bunch below the average with a long tail above it. The example slot shows the difference. Over 200 rounds of £1 it returns £192 on average, and the calculator's medium setting would give a range of £0.00 to £389.99. The exact distribution, computed from every possible outcome, has a median of £176: half of all sessions end below that. One in ten ends with £122 or less, one in ten with £253 or more, and 33% get at least the £200 back. Its exact standard deviation over those 200 rounds is £92.
Two patterns hold whatever the settings. As a share of stakes, the range narrows the longer you play, because the spread grows with √rounds while the stakes grow with rounds; the result drifts towards the RTP. In pounds, though, the range widens, and so does the average cost. Playing longer makes the outcome more predictable and more expensive at the same time.
What the calculator does not know
The calculator takes the RTP you enter at face value. A few things can make the real figure different. Some games are offered in several RTP versions, so check the figure in the game rules where you play. A progressive jackpot's contribution is usually counted in the RTP at its expected value, and since the jackpot almost never lands, the return most players experience is lower. Bonus rounds and features change volatility a great deal while leaving the RTP where it is.
It also cannot help anyone win. No input changes the house edge; the only levers are the RTP of the game chosen, the stake and the time spent. The house edge page explains where the margin comes from in every casino game, and the casino odds table puts the 4% of a 96% slot next to table games that keep less.
A budget worked out in advance is worth more than any figure here. If the numbers above look like money you would struggle to lose, or you notice yourself chasing a loss, the responsible gambling page has free, confidential help.
Related pages
RTP calculator: questions people ask
What does an RTP calculator work out?
The average amount a slot keeps from a given number of stakes. Multiply the stake by the number of rounds to get the total staked, then multiply that by the house edge (100% minus the RTP). The result is the long-run average cost, not what any single session will cost.
Is the expected cost what I will actually lose?
Rarely. It is the average across a very large number of sessions. Any one session can end well above or well below it, and with slots most sessions end somewhat worse than the average while a few end far better. The range shown alongside gives a rough idea of that spread.
Why does the calculator ask about volatility?
Volatility does not change the average cost, only how widely results spread around it. The calculator uses it to size the rough range: a high-volatility game can finish much further from the average than a low-volatility one with the same RTP.
What standard deviation does each volatility level use?
Low uses 3, medium 7 and high 15, each measured in stakes per round. Games do not publish this figure, so these are illustrative levels we chose. For comparison, the example slot on our slot odds page works out at 6.54.
How accurate is the range?
It is a rough guide based on a normal approximation, which works best over many thousands of rounds. Slot results are skewed, so for short sessions the true spread is lopsided: more sessions finish below the average than above it. Treat the range as an order of magnitude, not a promise.
Does a higher stake change the RTP?
No. The RTP is the same at any stake unless the game rules say otherwise, for example when a jackpot needs a particular stake. A higher stake scales the average cost in pounds by exactly the same factor.
How many rounds an hour should I enter?
It depends on how fast you play. Online slots in Great Britain must take at least 2.5 seconds per round, which caps an hour at 1,440 rounds; most people play slower than that, with pauses. Timing yourself for a few minutes gives a realistic figure.
Can I use it for games other than slots?
Yes, for any game with a fixed house edge. Enter 100% minus the edge as the RTP: 97.30% for a European roulette wheel, for instance. The volatility levels are designed around slots, so the range is less meaningful for table games.
Where do I find the RTP of a slot?
In the game's information, help or paytable screen, labelled "RTP", "return to player" or "theoretical return". Check it where you play, because some games are offered in several RTP versions.