RTP, RNG & House Edge, Explained

Last updated 2026-07-27 · Educational

Return-to-player (RTP) is the percentage of all wagered money a game is designed to pay back to players over the very long run. A slot with 96% RTP is built to return, on average, £96 for every £100 staked across millions of spins — not within any single session.

House edge is simply the mirror image

The house edge is 100% minus RTP. At 96% RTP the house edge is 4%. It is the mathematical margin that makes the operator, over time, the statistical winner — and the reason “the house always wins” in aggregate, even though individual players win and lose.

RNG: why each outcome is independent

A random number generator (RNG) produces each result independently of the last. A machine that has not paid out is not “due”; past outcomes carry no memory. In regulated markets, RNGs are tested and certified by independent laboratories (such as eCOGRA or GLI) before a game goes live.

Volatility

Volatility (or variance) describes how a game's payouts are distributed. Low-volatility games pay small amounts often; high-volatility games pay rarely but larger. Two games can share the same RTP yet feel completely different to play.

This page explains the mathematics as education. It is not a strategy guide, there is no game to play here, and no mathematics changes the fact that, over time, the house edge favours the operator.

Sources & notes

Concepts as defined by gambling regulators and testing bodies (e.g. UKGC guidance; independent test labs eCOGRA, GLI).
General mathematical treatment; no operator-specific figures.