Same RTP, different nights: an RTP and volatility simulator
Predict whether three slots with the same 96% RTP play alike, then compare 1,800 simulated sessions of each. You will see why RTP describes the average while volatility describes the session you are most likely to have.
How it works
Each slot is a two-outcome paytable that returns about $0.96 per $1 staked. Low volatility pays 1.2 times the stake on 60% of spins and 0.6 times on the rest; high volatility pays 3 times on 25% of spins and 0.28 times otherwise; the jackpot-style slot pays 320 times on 0.15% of spins and 0.481 times otherwise. Expected result per session = 150 spins × $1 × (RTP − 100%), about −$6 for each. What differs is the spread: the standard deviation per spin is about 0.29, 1.18 and 12.4 times the stake.
After your prediction, the tool plays 1,800 sessions of 150 $1 spins on each slot and drops every session's net result into a histogram. The three charts share one axis, from $90 down to $90 up, so their shapes compare directly, and results beyond either end are stacked in the outermost bar. A vertical line marks break-even and a small marker shows the average. Each card lists the share of sessions that ended ahead, the 'typical night' (the median session) and the worst and best results. The run uses fixed seeds, so every visitor sees the same histograms.
RTP is often read as a description of a normal session. In the tool's run the three averages sit within about $1 of each other, yet about 4% of low-volatility sessions, 36% of high-volatility sessions and 20% of jackpot-style sessions ended ahead. The jackpot slot's median session loses $78, because about four sessions in five never land the 320 times prize. The UK Gambling Commission says volatility is most commonly measured as a game's standard deviation, and that a highly volatile game might be made up of prizes that are 'very large but rare', while a low-volatility one mostly pays 'small and often'.
Volatility also decides how long the average takes to show. The Commission's guidance on monitoring live games uses a game's volatility to set the tolerance its actual return may show around the designed RTP: wide when little play has been measured, narrowing as play builds up. It calls a low-volatility game 'much more predictable' and says a highly volatile one 'will have a larger tolerance'. The difference is visible within a single 150-spin session here: the low-volatility histogram is a narrow spike, while the jackpot-style one splits between a large loss and a large win.
What it leaves out: Real slots have dozens of prize tiers, bonus features and progressive jackpots far larger than 320 times, so these two-outcome paytables show the principle rather than any real game, and the jackpot table actually returns 96.03%. For adults (18+) and purely educational, the simulator has no effect on the edge of any real slot.
Sources
Checked on 2026-11-05. Independent, not affiliated. 18+.
- UK Gambling Commission: Key terms relating to live return to player performance monitoring of games of chance (guide, last updated 28 January 2021)gamblingcommission.gov.uk
- UK Gambling Commission: How to calculate return to player (RTP), live RTP performance monitoring guide (last updated 25 January 2021)gamblingcommission.gov.uk
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