A short caution
Slot machines are games of chance with a built-in house edge. No strategy, system or timing changes the odds in the player’s favor over time, and most players lose money over time. Don’t gamble money you cannot afford to lose. If gambling is a worry for you or someone close to you, a local support service can help. A published return figure describes an average cost. It is not a promise of anything.
The definition
Return to player, usually shortened to RTP, is the percentage of all money wagered on a game that is expected to be paid back to players over the long run. If a game has an RTP of 95%, then across a very large number of spins, the game is designed to return 95 credits for every 100 wagered. The remaining 5 is the house edge, the average amount the operator keeps.
The figure is a theoretical one. It comes from the game’s math: the symbol weighting, the pay table, and the value of features. Designers can calculate it exactly in some games, and in others they estimate it with large-scale simulation, a method covered in the discussion of Monte Carlo simulation. Independent testing in regulated markets generally checks that the figure matches the game’s documentation.
A worked example
Take a hypothetical game with an RTP of 94%.
- If a player wagers 100 credits in total, the expected return is 94 credits, so the expected loss is 6.
- If a player makes 1,000 spins at 1 credit each, the total wagered is 1,000 credits. The expected return is 940, and the expected loss is 60.
- If a player makes 1,000 spins at 5 credits each, the total wagered is 5,000. The expected return is 4,700, and the expected loss is 300.
The word expected matters here. It means the average over very many repetitions, not what any one player will see. The relationship between the stake, the edge and the average loss is the idea of expected cost, and the same arithmetic is used for every casino game.
Notice that the percentage applies to total money wagered, not to the starting balance. A player who keeps re-staking winnings wagers far more than they deposited, so the expected loss is applied to a much larger total. This is part of why balances tend to fall faster than the headline percentage might suggest.
What RTP does not say
It does not describe a single session. A 94% RTP does not mean you will get 94 back from 100. In a short session, the actual result can be far above or below that figure. A player might win a large amount, or lose the entire stake much faster than the average implies. Short-term results scatter widely around the long-run figure, a spread that is described by game variance.
It does not say when you will win. The percentage gives no timing. A game with an RTP of 96% is not more likely to pay in the next ten spins than a game with 92%. Each spin is independent of the others.
It does not say how results are spread. Two games can have the same RTP and very different experiences. One might pay small amounts often, and another might pay rarely and in large amounts. The difference between them is explained in the comparison of hit frequency and payout size.
It does not include what you do with winnings. RTP is calculated as if every credit were wagered at the same rate. In practice, many players leave when ahead, but that does not change the number: whatever was wagered still carries the average cost.
It does not reset or adjust. There is no cycle in which a game returns the missing percentage after a run of losses. The idea that a machine is behind on its payout and owes players is addressed in the article on due machines.
It is not a guarantee about any machine on a floor. In some settings, an operator can choose between different return settings for the same game, within limits set by the regulator, so two copies of the same title may differ. The published figure applies to the version in question.
Reading an RTP figure sensibly
The most useful comparison is cost. A higher RTP means a lower expected cost per credit wagered, all else equal. But the amount lost per hour also depends on how many credits are wagered per hour, which depends on bet size and the speed of play. A 97% game played at a high speed and high stake can cost more per hour than a 92% game played slowly at low stakes. Comparing the cost per hour is therefore more informative than comparing percentages alone.
RTP also needs to be read with the features included. The figure usually covers the whole game, base spins plus bonus features and jackpots. Where a progressive prize is part of the game, some of that return is tied up in a very rare event, a point covered in the explanation of how bonus rounds count toward the total.
How it relates to the house edge
RTP and the house edge are the same number seen from opposite sides: add them and you get 100%. A 94% RTP is a 6% edge. The relationship is explained in more detail in the article on house edge versus RTP. Both describe an average over a large number of plays, and neither is a prediction for the night.
The takeaway
RTP is a useful number because it tells you the average price of the entertainment. It is a poor number for predicting what will happen on a given day. Treat it as a cost estimate, set a limit before you play, and expect that over time the average will win.