RTP (return to player) is the percentage of all wagered money that a slot pays back over its lifetime. A 96% RTP slot returns £96 for every £100 wagered — but this is averaged over millions of spins, so any individual session can vary wildly. This calculator helps you compare theoretical RTP against your actual session results to identify high-variance play and to know when you're being misled by short-term variance.

Enter your total wagered amount, total won, number of spins, and the slot's published RTP. The calculator returns your actual session RTP, the variance from theoretical RTP, the standard deviation you should expect, and the probability of seeing results at least as extreme as yours. A session at 60% RTP after 100 spins on a 96% slot is statistically normal (about 16% probability). A session at 60% RTP after 10,000 spins suggests something else is going on.

Slots with published RTP below 94% should be avoided by anyone playing for value. UKGC-regulated casinos must publish RTP for every slot — if you can't find it on the casino site or the game provider's spec page, that's a red flag. We maintain a database of slot RTPs at /slots — cross-reference before playing.