Expected loss per hour is your bet per spin, times the spins you play in an hour, times the game’s house edge. At $1 a spin, 10 spins a minute and a 96% RTP game, that is $1 × 600 × 4% = $24 an hour. The session and bankroll calculator shows it for your own figures.
The formula and a worked example
House edge = 1 − RTP
Expected loss per hour = bet × spins per minute × 60 × house edge
The house edge is the share of every bet the game keeps on average; the Wizard of Odds defines it as the ratio of the average loss to the initial bet. For a slot it is 100% minus the RTP.
| Input | Value |
|---|---|
| Bet per spin | $1 |
| Spins per minute | 10 (600 an hour) |
| RTP | 96%, so a 4% house edge |
| Amount bet in an hour | $600 |
| Expected loss per hour | $600 × 0.04 = $24 |
This is the same figure people call theoretical loss. It does not depend on your bankroll, how you feel about the machine or how the last hour went. It depends only on how much you put through the game and the game’s edge.
Pace matters as much as RTP
Because the cost scales with spins per hour, a faster game can cost more than a lower-RTP game played slowly. At $1 a spin:
| Game | RTP | Pace | Expected loss per hour |
|---|---|---|---|
| A | 97% | 15 spins a minute | $27 |
| B | 95% | 6 spins a minute | $18 |
Game A has the better RTP and still costs $9 more an hour, because it is played two and a half times as fast. How fast slots play covers pace in detail, including the quick-spin settings that speed play up.
How each input moves the cost
Every input is a straight multiplier, so doubling any one doubles the hourly cost.
| Change | From | To | Hourly cost at the other default values |
|---|---|---|---|
| Bet per spin | $1 | $2 | $24 to $48 |
| Spins per minute | 10 | 5 | $24 to $12 |
| RTP | 96% | 98% | $24 to $12 |
| RTP | 96% | 92% | $24 to $48 |
Notice the asymmetry in how RTP looks and how it costs. Moving from 96% to 98% sounds like a 2% improvement. It halves the hourly cost, because the house edge drops from 4% to 2%.
Why one hour can look nothing like the average
The expected loss is an average over many hours. A single hour of slots is short, and slot results are lopsided: most hours lose somewhat more than the average, and a few hours with a big win lose much less or come out ahead. On a high-volatility game, an hour can easily swing by many times the $24 average in either direction.
That is why the calculator pairs the averages with a simulation of how long real sessions last. Volatility explains the spread, and the RTP and volatility simulator shows it for any session length.
Using the hourly figure
Treat the expected loss per hour as the price of the session, then decide whether it is worth it in the same way you would judge a concert ticket. If $24 an hour is more than you want to spend, change the bet, the pace or the game before you start. Then set a loss limit and a time limit you will hold to, ideally with the casino’s own limit tools: setting session limits covers what is available.
Common questions
Is the expected loss per hour what I will actually lose?
No. It is the average across a very large number of hours. Any single hour can end well up or well down, and on a volatile game the swing in one hour is usually much larger than the expected loss. The figure is a price tag for planning, not a forecast.
What is theoretical loss?
Theoretical loss is another name for expected loss: the total amount bet multiplied by the house edge. It is called theoretical because it describes the long-run average, not what happened in any one session.
How can I lower my cost per hour on slots?
Lower the bet, slow the pace or choose a game with a higher RTP. Halving any one of bet size, spins per hour or house edge halves the expected loss per hour. Bet size is usually the easiest lever.