How to use the calculator
- Bankroll: the money you are prepared to lose in this session. Not your account balance, and not money you need.
- Bet per spin: the total stake per spin, across all lines.
- Game RTP: the return to player shown in the game’s help or paytable screen. What RTP means covers where to find it and why one game can have several versions.
- Spins per minute: your real pace. Count a minute of your own play. Autoplay and quick-spin settings run faster than hand play, and a faster pace costs more per hour. How fast slots play explains why.
The results update as you type. The volatility setting only affects the spread in the lower panel, never the averages.
The formula, step by step
House edge = 1 − RTP
Expected loss per spin = bet × house edge
Expected loss per hour = loss per spin × spins per minute × 60
Average spins until the bankroll is gone = bankroll ÷ loss per spin
Average total bet (turnover) = bankroll ÷ house edge
The default figures are a $200 bankroll, $1 a spin, a 96% RTP game and 10 spins a minute.
| Result | Working | Value |
|---|---|---|
| Expected loss per spin | $1 × 0.04 | 4 cents |
| Expected loss per hour | $0.04 × 10 × 60 | $24 |
| Average spins | $200 ÷ $0.04 | 5,000 |
| Average time | 5,000 ÷ 10 a minute | 8 hours 20 minutes |
| Average total bet | $200 ÷ 0.04 | $5,000 |
| Shortest session, no wins | $200 ÷ $1 | 200 spins, 20 minutes |
The average-spins line assumes you put every win back in and stop only when less than one bet is left. That is the honest way to measure what a bankroll buys. It comes from a result in probability known as Wald’s identity: when you play until the money runs out, the total you lose equals the number of spins times the average loss per spin. Your $200 bankroll passes $5,000 through the machine before it is gone, on average, because wins keep feeding it back in.
Why most sessions are shorter than the average
The 5,000-spin average is real, but it is not typical. The calculator’s lower panel replays the bankroll a thousand times on a model slot. At the default settings:
| Model slot | Shortest 10% end by | Median session | Longest 10% last at least |
|---|---|---|---|
| Low volatility | 1,445 spins (about 2 hr 25 min) | 3,624 spins (about 6 hr) | 10,878 spins (about 18 hr) |
| Medium volatility | 571 spins (57 min) | 1,473 spins (about 2 hr 27 min) | 12,098 spins (about 20 hr) |
| High volatility | 342 spins (34 min) | 619 spins (about 1 hr) | 3,220 spins (about 5 hr 20 min) |
On the high-volatility model, half of all $200 sessions are over in about an hour, against an 8-hour average. The average stays at 5,000 spins because a small number of sessions hit a big win and run for a very long time. Every model slot has the same 96% RTP. Volatility does not change what you lose on average. It changes how that loss is spread: volatility explains the mechanism.
The two levers: bet size and RTP
Bet size moves the result far more than anything else you control. The table keeps a $200 bankroll, a 96% game and 10 spins a minute.
| Bet per spin | Average spins | Average time | Expected loss per hour | No-win floor |
|---|---|---|---|---|
| $0.20 | 25,000 | 41 hr 40 min | $4.80 | 1,000 spins |
| $0.50 | 10,000 | 16 hr 40 min | $12 | 400 spins |
| $1 | 5,000 | 8 hr 20 min | $24 | 200 spins |
| $2 | 2,500 | 4 hr 10 min | $48 | 100 spins |
| $5 | 1,000 | 1 hr 40 min | $120 | 40 spins |
RTP matters too, and more than its small-looking gaps suggest, because the house edge is what you pay. At $1 a spin, a 98% game costs $12 an hour and a 92% game $48: four times as much for a 6-point difference in RTP.
| Game RTP | House edge | Expected loss per hour | Average time on $200 |
|---|---|---|---|
| 92% | 8% | $48 | 4 hr 10 min |
| 94% | 6% | $36 | about 5 hr 33 min |
| 96% | 4% | $24 | 8 hr 20 min |
| 98% | 2% | $12 | 16 hr 40 min |
Choosing a bet size for your bankroll turns these numbers into a working rule of thumb.
Using the result to plan a session
Treat the expected loss per hour as the price of the entertainment, the way you would price a movie or a round of golf. If $24 an hour is more than the evening is worth to you, lower the bet or pick a higher-RTP game before you start, not after a losing run.
Then set the stop before you play. A loss limit (the bankroll), a time limit and a decision about what you will do with a win all work better made in advance. State rules in New Jersey and Pennsylvania, for example, require licensed online casinos to offer limit tools that hold you to them: setting session limits covers what they are and how they work. Expected loss per hour explains the hourly figure and how to use it to compare games.
Common questions
How long will $100 last on slots?
At $1 a spin on a 96% RTP game, $100 lasts 2,500 spins on average if you keep replaying wins, which is a little over four hours at 10 spins a minute. With no wins at all it lasts 100 spins. Most real sessions end well before the average, because a few very long sessions pull the average up.
What is theoretical loss on a slot?
Theoretical loss is the amount you are expected to lose on average, worked out as total amount bet multiplied by the house edge. At $1 a spin, 600 spins an hour and a 4% edge, it is $24 an hour. It is an average across many sessions, not a prediction of any one.
Does a bigger bankroll improve my chances on slots?
It does not change the house edge or your expected loss per spin. It only lets you play longer, which means more total betting and a larger expected loss in dollars. What it does change is how often you go broke before a planned stopping point.
The terms, explained
- 01 Expected Loss Per Hour on Slots Bet times spins per hour times house edge: the hourly price of a slot session, and why pace matters as much as RTP.
- 02 Choosing a Bet Size for Your Slot Bankroll Think in bets, not dollars: how many bets your bankroll holds decides whether a session lasts the evening.
- 03 How Fast Slots Play, and Why Speed Costs Money Twice the spins per hour means twice the expected loss. How to measure your pace and what the rules say about speed.
- 04 Setting Session Budgets and Loss Limits The deposit, spend and time limits licensed casinos must offer, how fast changes take effect, and how to size them.