Two numbers govern the maths of every casino game. Understand them and you understand what a game really costs — and why the house always keeps an edge.
RTP — return to player — is the share of all stakes a game is built to return over the long run. The gap up to 100% is the house edge: the casino’s margin. A 96% RTP slot has a 4% house edge, so across a very large number of spins it pays back about £96 per £100 staked and keeps £4. They’re the same fact from two directions — the return you see, and the cost you pay. Turn a percentage into pounds for your own stake with the RTP & expected-loss calculator.
RTP is a long-run average over millions of spins — it says nothing about what happens in your session. That short-term spread is volatility: two games can share a 96% RTP yet feel completely different, one paying small and often, the other rarely but big. The house edge is the tide; volatility is the waves. Over a long session your results grind toward the edge (an expected loss); over a short one, anything can happen.
Use RTP to compare the long-run cost of games and to set a realistic budget — a higher RTP means a smaller expected loss over time. Don’t use it to predict a session or chase a “due” win: every spin is independent and random, and no RTP makes the expected result anything other than a loss. That honesty is the whole point — see how each of our slot pages labels RTP as provider-published and variable, never an Atlas-verified promise.
Reflects standard industry practice and UK-licensed game testing — July 2026. Informational, not advice. 18+.
What does RTP mean?
RTP (return to player) is the percentage of all stakes a game is designed to pay back over the very long run. A 96% RTP means that, across millions of spins, the game returns about £96 for every £100 staked — leaving a 4% house edge. It is a long-run average, not a promise for any one session.
What is the house edge?
The house edge is simply 100% minus the RTP — the casino's built-in mathematical margin. At 96% RTP the house edge is 4%. It applies to every bet, which is why, the longer you play, the closer your results drift toward an expected loss.
Is a slot's RTP guaranteed?
No. RTP is a theoretical figure that only holds over enormous numbers of spins. Any real session can win or lose far more than the average — that spread is the game's volatility. RTP tells you the long-run cost, not what will happen tonight.
How is RTP tested and can casinos change it?
The random number generator and the stated RTP are tested by independent labs (such as eCOGRA, GLI or iTech Labs) before a game goes live. However, some providers ship a game in several RTP versions, and operators choose which to run — so the figure that applies to you is on the game's own info screen.