RTP and Volatility Simulator

How to use the simulator

Set the four inputs and the table redraws. Every run plays the same session on all three model slots, so you can compare them side by side.

• RTP: from 80% to 99.5%. All three models are tuned to it exactly.
• Bet per spin and starting balance: a session stops early if the balance falls below one bet, just as it would in a real game.
• Spins: up to 20,000. At 10 spins a minute, 1,000 spins is about an hour and forty minutes.

The headline figure is the average cost the RTP predicts: spins × bet × (1 − RTP). It is the same for every model. The chart and table show what actually happened across the simulated sessions. “Replay with new random spins” runs a fresh set, so you can see how much the results themselves move from run to run.

What the default run shows

The default is 1,000 spins at $1 on a 96% RTP game, starting with $200. The RTP says the average session costs $40 and ends at $160.

Three things stand out.

1. The low-volatility model behaves like the average. Its median session ended close to the $160 the RTP predicts, and almost nobody went broke. It also rarely produced a big result: its largest possible win is 25 times the bet.
2. The high-volatility model splits sessions into two groups. Three in four went broke inside 1,000 spins. A few found one of the large prizes and finished well ahead. Its median session ended with less than one bet left.
3. The averages differ for one reason only. Across all sessions, the low model lost about $40.50 each, almost exactly what the RTP predicts. The medium model lost about $34 and the high model about $12. The gap comes from sessions that went broke: a session that runs out stops betting, so it stops paying the house edge. It is not an advantage. It is what running out of money looks like, and most of those sessions ended with nothing.

The three model slots

Each model is a simple payout table: a list of possible wins, each a multiple of the bet, with a chance per spin. At their base settings all three return exactly 96%. To reach another RTP, the simulator scales the chance of every win by the same factor, so the shape of each game stays the same and only the share of losing spins moves.

They are teaching models built to show three clearly different shapes of risk. They are not copies of any real game, and real games are far more complicated, with bonus rounds, multipliers and features that change from spin to spin.

Low volatility. A win on about 40% of spins, top prize 25 times the bet. The standard deviation of one spin’s result is about 2.4 bets.

Medium volatility. A win on about 31% of spins, top prize 250 times the bet. Standard deviation about 6.5 bets.

High volatility. A win on 25% of spins, top prize 5,000 times the bet. Standard deviation about 27 bets.

Notice where the return comes from. On the low model, half of the 96% comes from wins of 5x or less. On the high model, 13% of the 96% comes from a prize you would expect to see about once in 38,000 spins. Most sessions never see it, so most sessions do worse than the RTP. Some 0.5x and 1x “wins” do not even return the bet: hit frequency covers why that matters.

The formula, step by step

Two numbers describe a session before it starts: the average cost and the typical spread around it.

Here σ is the standard deviation of a single spin, in bets: about 2.4, 6.5 and 27 for the three models. The cost grows in step with the number of spins. The spread grows only with its square root. So over a short session the spread swamps the cost, and over a long enough run the cost wins.

The spread is a guide, not a hard range: slot results are lopsided, with a long tail of rare big wins, so the median sits below the average and the range is far from symmetrical. The simulator shows the real shape. Why RTP only shows up over many spins walks through this in more detail.

What a model can and cannot tell you

A model shows the shape of risk honestly: same price, very different rides. It cannot tell you the volatility of a real game, because a game’s paytable shows what each combination pays but not how often it lands. Some studios show a volatility rating in the game information, and the paytable itself gives clues: very large top prizes and long gaps between bonus rounds point to high volatility. Slot volatility explained covers how to read those signs.

Nothing here can make a slot a winning bet. Every model, at every setting below 100% RTP, loses on average. The simulator is for choosing a game, a bet and a budget that match the session you want, with the cost in plain view.