A slot machine calculator turns four numbers into one: the average amount a slot session costs. You enter the stake per spin, the spins per hour, the hours you play and the house edge, and the tool above multiplies them to show what the machine keeps on average over many sessions.
Below you will find how to read the number, how RTP becomes a house edge, what spin speed does to the cost, and why one real session can look nothing like the average. Every figure is computed from a formula you can check, with its assumptions named.
What does a slot machine calculator show?
A slot machine calculator shows the expected cost of a session: the average amount the machine keeps from what you stake. It multiplies stake per spin, spins per hour and hours played, then applies the house edge. With the starting values (1 unit, 500 spins an hour, 2 hours, 8% edge), 1,000 units are staked and the expected cost is 80 units.
Expected means an average over a very large number of sessions, not a forecast for tonight. Cost is the net amount that stays with the machine after all wins are paid, so it already includes every prize you collect. The tool does not know which machine you are on. You supply the edge, and the result is only as good as that number.
The same formula drives our general gambling session cost calculator. This page goes further on slots: how return to player (RTP) maps to the edge, how fast spins come, and how lumpy slot results are.
How do you use the slot machine calculator?
Enter four numbers and read the expected cost. Stake per spin is the total bet on one spin, spins per hour is how fast you play, hours played is the session length, and house edge is 100 minus the machine’s RTP. Stake and hours accept decimals, so 1.5 means an hour and a half.
- Stake per spin. Use the total bet for one spin, not the coin or credit value. If a spin uses 50 credits and each credit is worth 0.01 units, the stake is 0.50 units.
- Spins per hour. Count how many spins you make in an hour. If you are unsure, try 300, 500 and 720, then see the speed table below.
- Hours played. Enter the length of the session you are planning or just finished.
- House edge. Enter 100 minus the RTP. An RTP of 92% means an edge of 8%. The box accepts 0 to 30.
- Read the result. The big number is the expected cost. The line under it shows the total staked, and the bar shows the edge on a scale of 0 to 30%.
Example: You plan 3 hours at 2 units a spin, 600 spins an hour, on a game with a 95% RTP. The edge is 100 – 95 = 5%. Total staked = 2 x 600 x 3 = 3,600 units. Expected cost = 3,600 x 5 / 100 = 180 units, which is 60 units an hour.
Which mistakes make the result wrong?
- Typing the RTP in the edge box. Enter 8, not 92. The box stops at 30, so 92 is rejected.
- Entering the money you brought instead of the money you stake. The edge applies to the total staked, which can be many times your bankroll (see the section on turnover below).
- Guessing spin speed low. At 1 unit a spin and an 8% edge, 300 spins an hour costs 24.00 units an hour and 1,440 spins an hour costs 115.20.
How do you turn RTP into a house edge?
House edge equals 100% minus RTP. RTP, short for return to player, is the share of all money staked that a game pays back on average over a very long run. A slot with a 92% RTP keeps 8% on average, so every 100 units staked costs 8 units. RTP and house edge describe the same fact from opposite sides.
This table converts RTP values to house edge and shows the average cost for every 1,000 units staked. The 75% row is a regulatory minimum covered in a later section, not a typical machine.
| RTP | House edge (100 minus RTP) | Average cost per 1,000 units staked | Average paid back per 1,000 units staked |
|---|---|---|---|
| 98% | 2% | 20.00 | 980.00 |
| 96% | 4% | 40.00 | 960.00 |
| 94% | 6% | 60.00 | 940.00 |
| 92% | 8% | 80.00 | 920.00 |
| 90% | 10% | 100.00 | 900.00 |
| 88% | 12% | 120.00 | 880.00 |
| 85% | 15% | 150.00 | 850.00 |
| 75% | 25% | 250.00 | 750.00 |
RTP covers the whole game: base spins, bonus rounds, free spins and any jackpot share. It is a share of money staked, not of money you bring, so a 92% RTP does not mean you get 92 back from every 100 you walk in with. For comparison, a single-zero roulette wheel has an edge of 1 in 37, or 2.70%, as the roulette odds and payouts guide shows.
Where can you find the RTP of a slot machine?
Look for the game’s published RTP, which regulators and some health programs report. In Great Britain, the Gambling Commission’s remote technical standards on game information require the RTP percentage, or the probability of winning events, to be easily available before a customer commits to gamble. For physical machines, rules usually set a minimum rather than a label.
Two examples of minimums. Nevada’s Regulation 14, section 14.040(1)(a), in the 2016 version we read, requires a gaming device to theoretically pay out a mathematically demonstrable percentage of amounts wagered that is not less than 75% for each wager available. That allows an edge of up to 25%. A minimum is a floor, not a measurement of the machine in front of you, so a figure for your machine, if one is shown, beats a range.
When no figure is shown, use published ranges and test a few edges. The Manitoba GameSense cost of play chart for slots and video lottery terminals uses a house advantage of 9% for penny, 2 cent and nickel machines, 8% for quarter machines, 5% for dollar machines and 7% for video lottery terminals, and says the figure may vary by plus or minus 3 points. Those are one program’s figures for one province, not a rule for every machine. In the calculator, try the figure plus and minus 3 points.
You cannot work out a machine’s RTP by watching it for a few hours. As the simulation below shows, the luck in one session swamps the edge, so a short run says almost nothing about the published figure.
How many spins per hour does a slot machine take?
It depends on the player and the game. The one hard limit we found is for online slots in Great Britain: the Gambling Commission’s responsible product design standard (RTS 14D) says a spin must take at least 2.5 seconds, a cap of 3,600 / 2.5 = 1,440 spins an hour. The GameSense charts use 720 an hour, a spin every 5 seconds.
Speed is the input people forget. Each spin is another stake the edge applies to, so doubling the speed doubles the cost at the same stake and RTP. This table shows five speeds at 1 unit a spin and an 8% edge. The 720 and 1,440 figures come from the published sources above. A peer-reviewed study of gambling data, Harris and Griffiths (2018, Journal of Gambling Studies), reports a typical industry standard of about 3 seconds per slot event (roughly 1,200 an hour) and average rates of about 8 spins a minute (480 an hour) for regular gamblers and 6 a minute (360 an hour) for non-regular gamblers. The 300, 500 and 1,000 rows are our own round figures placed around those ranges for illustration.
| Spins per hour | Seconds per spin | Average cost per hour (1 unit, 8% edge) | Average cost for 2 hours | Where the speed comes from |
|---|---|---|---|---|
| 300 | 12.0 | 24.00 | 48.00 | Our assumption, below the 360 an hour reported for non-regular gamblers |
| 500 | 7.2 | 40.00 | 80.00 | Our assumption, close to the 480 an hour reported for regular gamblers (Harris and Griffiths 2018) |
| 720 | 5.0 | 57.60 | 115.20 | GameSense Manitoba chart speed |
| 1,000 | 3.6 | 80.00 | 160.00 | Our assumption, below the roughly 1,200 an hour implied by a 3-second event (Harris and Griffiths 2018) |
| 1,440 | 2.5 | 115.20 | 230.40 | Online cap under UK rule RTS 14D |
How much does a slot machine cost per hour?
Cost per hour is the stake times the spins per hour times the edge. At 720 spins an hour, a 1 unit spin on a 92% RTP game costs 57.60 units an hour on average. The same spin at 96% RTP costs 28.80, and at 85% it costs 108.00. Doubling the stake doubles every figure.
This grid shows the average cost per hour in units at 720 spins an hour, by stake per spin and RTP. It is the table the tool produces if you run each pair one at a time.
| Stake per spin (units) | Staked per hour | Cost per hour at 96% RTP | Cost per hour at 94% RTP | Cost per hour at 92% RTP | Cost per hour at 90% RTP | Cost per hour at 88% RTP | Cost per hour at 85% RTP |
|---|---|---|---|---|---|---|---|
| 0.25 | 180.00 | 7.20 | 10.80 | 14.40 | 18.00 | 21.60 | 27.00 |
| 1 | 720.00 | 28.80 | 43.20 | 57.60 | 72.00 | 86.40 | 108.00 |
| 2 | 1,440.00 | 57.60 | 86.40 | 115.20 | 144.00 | 172.80 | 216.00 |
| 5 | 3,600.00 | 144.00 | 216.00 | 288.00 | 360.00 | 432.00 | 540.00 |
| 10 | 7,200.00 | 288.00 | 432.00 | 576.00 | 720.00 | 864.00 | 1,080.00 |
| 25 | 18,000.00 | 720.00 | 1,080.00 | 1,440.00 | 1,800.00 | 2,160.00 | 2,700.00 |
Two things stand out. First, the amount that passes through the machine is large even at small stakes: 0.25 units a spin stakes 180 units an hour. Second, a few points of RTP matter a lot: at a 5 unit stake, moving from 96% to 88% RTP lifts the cost from 144.00 to 432.00 units an hour.
Why does the house edge apply to your total staked, not the money you bring?
Because the edge is a share of every spin’s stake, and winnings go back into the machine. If you keep playing until you cannot cover another spin, the average total staked is about the bankroll divided by the edge: 100 / 0.08 = 1,250 units for a 100 unit bankroll at an 8% edge.
Each unit staked costs 0.08 units on average, so it takes about 1,250 units staked to lose 100. At 720 spins an hour that is 1,250 / 720, about 1.7 hours. At 500 spins an hour it is 2.5 hours. That is why the calculator asks for stake, speed and time, not a bankroll.
We checked the rule with the simulation described in the next section. With a 100 unit bankroll and 1 unit spins, the average number of spins before the money ran out was 1,252 (Steady model) and 1,250 (Streaky model), in line with 1,250. The median run was much shorter: about 790 spins and 260. The average hides how uneven the paths are.
Why can one slot session end far from the expected cost?
Because the expected cost is an average, and slot results are lumpy: many small losses and a few large prizes. In our simulation of 1,000 spins at 1 unit, the middle half of sessions ended between -147 and -48 units in the Steady model and between -350 and +87 in the Streaky model, both with a 92% RTP.
How we built it. We invented two pay models. They are not real machines, and we do not claim to know the volatility of any real game. Each returns exactly 92% of stakes on average. The Steady model pays something on 63.4% of spins and has a top prize of 200 times the stake. The Streaky model pays something on 32.0% of spins and has a top prize of 2,000 times the stake. We simulated 1,000,000 sessions of 1,000 spins for each (Python, fixed random seed). Results are per 1 unit stake, so multiply by your stake. At 720 spins an hour, 1,000 spins is about 1.4 hours.
This table shows the spread of net results after 1,000 spins of 1 unit, in units. Negative numbers are losses. Percentile means the share of sessions at or below that result.
| Result after 1,000 spins | Steady model | Streaky model |
|---|---|---|
| Expected result (the average) | -80 | -80 |
| 5th percentile (1 session in 20 ended here or worse) | -196 | -457 |
| 25th percentile | -147 | -350 |
| Median (the typical session) | -107 | -236 |
| 75th percentile | -48 | +87 |
| 95th percentile (1 session in 20 ended here or better) | +122 | +689 |
| Sessions that ended ahead | 18.4% | 29.2% |
| Sessions that lost more than 160 (twice the expected cost) | 17.8% | 61.1% |
| Standard deviation (spread of results) | about 103 | about 459 |
Read the Streaky column twice. Its average is -80, yet its typical session (the median) is -236, almost three times worse, because a few very large prizes pull the average up. Still, 29.2% of its sessions ended ahead, and 61.1% lost more than double the expected cost. The average is real, but it describes no single session well.
Length changes the picture. In the Steady model, 22.3% of 100-spin sessions ended ahead but only 0.1% of 20,000-spin sessions did (about 28 hours at 720 spins an hour), as the edge takes over. In the Streaky model, rare large prizes kept 20.5% of 20,000-spin sessions ahead, yet most sessions there still lose more than the average. Neither model tells you what a real game will do.
Do hit frequency, bonus rounds and near misses change the cost?
No. Hit frequency, bonus rounds and free spins are already built into the RTP, so they change how the cost arrives, not how large it is. Two games with the same RTP, stake and speed cost the same on average. What differs is how often something pays and how uneven the ride is.
Hit frequency is the share of spins that pay anything. In our models it was 63.4% for the Steady one and 32.0% for the Streaky one, and both cost 8% of the amount staked. A high hit frequency can mislead: in the Steady model, 22 of every 100 spins pay 0.5 units on a 1 unit spin, which is a win on screen but half the stake lost. Only 41.4% of its spins paid back at least the stake.
Bonus rounds and free spins are part of how the RTP is paid out. A game quoted at 96% RTP counts the bonus inside that 96%. You cannot add the value of a feature on top of the quoted figure.
Near misses do not change the cost either, but they change how a spin feels. In a 2009 study in Neuron, Clark and colleagues (repository record of the paper) reported that near misses on a slot machine task activated reward areas of the brain that also respond to wins, and increased the wish to keep playing. A near miss is still a loss, and the edge is unchanged.
Hot and cold machines are a feeling, not a mechanism. When spins are independent, a past result says nothing about the next one. Under Great Britain’s remote technical standards on random outcomes (RTS 7A), adaptive behavior, that is a compensated game, is not permitted, so an online slot there may not change its probabilities in response to what has happened. The belief that a loss makes a win due is the gambler’s fallacy.
What should you do with your result?
Compare the expected cost with what you planned to spend, and set a money limit and a time limit before you start. If the number is higher than you expected, lower the stake, slow down or play for less time. The estimate is an average, so a real session can cost more than it shows.
- Run the session you have in mind. Use your real stake, pace and planned time.
- Test the edge. If you do not know the RTP, run 5%, 8% and 12% and plan around the highest result.
- Set the limit first. Decide the most you will spend and when you will stop, then keep to both.
- Compare with what you actually spend. A gambling spend tracker shows whether real sessions match the estimate, and an expected loss calculator covers other bet types.
If you spend more than you planned, or stopping feels hard, the Safer play toolkit is a good place to start, and the Get help page lists services you can contact.
How to read the result
The large number is the expected cost: the average amount the machine keeps from your total staked, after all wins are paid. The line under it shows the total staked, which is stake per spin times spins per hour times hours played. The bar shows the house edge on a scale of 0 to 30%. House edge is 100 minus the RTP, so an RTP of 92% is an edge of 8%. Typical values depend on the game and place: published program figures for slots run from about 5% to 9% (Manitoba GameSense), and a legal minimum payout of 75% allows an edge of up to 25%. Spin speed changes the cost in proportion, so doubling spins per hour doubles the result. The expected cost is an average over many sessions. One session can cost far less or far more.
How it is calculated
Total staked = stake per spin x spins per hour x hours played. Expected cost = total staked x house edge / 100. House edge = 100 - RTP. The calculator multiplies the first three inputs, applies the edge, and shows the cost, the total staked and the edge. It does not model wins, losing streaks, bonus features or stakes that change during the session. The tool's check line for the starting values reads 1.00 x 500 x 2.0 x 8.00% = 80.00.
Worked example
Worked example
With the starting values: stake 1 unit, 500 spins per hour, 2 hours, house edge 8% (an RTP of 92%). Total staked = 1 x 500 x 2 = 1,000.00 units. Expected cost = 1,000 x 8 / 100 = 80.00 units. The tool shows 80.00 units as the expected cost, 1,000.00 units staked and a house edge of 8.00%. Raise the speed to 720 spins per hour and the cost becomes 1 x 720 x 2 x 8 / 100 = 115.20 units. This is an average over many sessions, not a prediction for one.
Limits
The result is a long-run average, not a forecast. A single session can end ahead or cost several times the estimate. The tool assumes one fixed stake, one fixed speed and one fixed house edge for the whole session. It does not know the real RTP of any machine, so a wrong edge gives a wrong answer, and a game can be published in versions with different RTPs. It does not model bonus features, extra-cost options, jackpots, changing stakes, tips, food, travel or tax. It does not round the way a machine may. Inputs are limited to a stake of at least 0.01, at least 1 spin per hour, at least 0.1 hours and an edge from 0 to 30%. Results are estimates, not advice.