Slot machine house edge

What the slot machine house edge is

Every slot is built to return a little less than it takes in. The part it keeps is the house edge. The part it gives back is the return to player, or RTP. The two always add up to 100%, so if you know one you know the other: a 95% RTP game has a 5% edge, a 97% game a 3% edge.

House edge is a long-run average across millions of spins and many players. It doesn’t mean the machine takes exactly 4p from each £1 you put in. On a single spin you either lose the stake or win something, and over a short session you may finish well up or well down. What the edge does give the operator, given enough play, is a steady margin. For you, it is the price of the entertainment.

This page is part of our guide to how slot machines work.

How the house edge is built into a slot machine

A slot doesn’t take a fee from each spin the way a bookmaker’s margin or a commission might. The edge is hidden inside the paytable. Each prize pays slightly less than the true odds of hitting it would justify, and the gap across all prizes is the house edge.

Take one made-up prize to see the idea. Suppose a combination has a 1 in 500 chance of landing on any spin. A “fair” game, with no edge at all, would pay 500 times the stake for it, because over 500 spins you would stake 500 units and get 500 back. If the paytable pays 450 instead, that prize returns 90% of its fair value. Designers set every prize, including features and free spins, so that the weighted total comes out at the target RTP.

Real games mix hundreds of prizes, but the principle is identical. The random number generator picks outcomes fairly according to their probabilities; the edge comes from what each outcome pays, not from cheating on which outcome appears. That is why a game can be both fair, in the sense of being random and as described, and still certain to cost money on average.

House edge on popular UK online slots

Developers publish RTP in each game’s help screen, so the house edge is easy to work out. The figures below come from the developers’ own published RTPs for the versions listed; casinos may run a lower-RTP version of some games, so always check the help screen of the game in front of you.

Jackpot games are a special case. Part of each stake feeds a prize pool, and developers may quote RTP with or without that contribution. Mega Moolah, for example, is listed at 88.12% for the base game excluding the jackpot contribution, so its base-game edge looks large because some of the return sits in the progressive pot. Our guide to how slot jackpots are funded explains the split.

Many modern games also come in several RTP variants. Big Bass Bonanza’s bigger sibling, Bigger Bass Bonanza, is listed at 96.71% with 95.67% and 94.62% versions also in circulation. Moving from the top to the bottom version raises the edge from 3.29% to 5.38%, which on £100 of spins is £2.09 more in average cost.

Slot house edge in pounds: cost per spin and per 100 spins

Percentages are abstract, so convert them. Average cost = total staked × house edge. The stake per spin and the number of spins are what turn a small-sounding percentage into real money.

The £2 and £5 rows reflect the UK online slot stake limits: since 9 April 2025 the maximum is £5 a spin for players aged 25 and over, and since 21 May 2025 it is £2 for those aged 18 to 24, as set out in the Gambling Commission’s online slots stake limit guidance (opens in a new tab).

How spin speed turns the edge into an hourly cost

The edge is charged on every spin, so the faster you play, the more it costs per hour. UK-licensed online slots must take at least 2.5 seconds per spin and can’t offer autoplay or turbo modes, rules covered on our spin speed rule page. That caps play at 1,440 spins an hour (3,600 seconds ÷ 2.5). Most people play slower, pausing between spins and during features.

These are averages over a very long run; a real hour could produce a big win or lose much more than the figure shown, especially on high-volatility games. For more examples, see how much a slot costs per hour.

Why a small edge eats a budget: recycling winnings

A 4% edge sounds gentle until you notice that it applies to every pound staked, not just the pounds you deposit. When you win and keep spinning, those winnings are staked again and the edge takes its share once more. This churn is why total stakes in a session are usually several times the starting balance.

A worked example: you start with £50 and play 50p spins on a 96% game. If you play until the balance runs out, the average total staked is about £50 ÷ 0.04 = £1,250, or roughly 2,500 spins. You may hit wins along the way, but on average the edge consumes the whole £50 over that much play. Stopping earlier, with a fixed time or loss limit, is the only reliable way to keep the cost down. Our bankroll guide and the glossary entry on theoretical loss show how operators and players measure this.

Slot house edge vs other casino games

Slots usually carry a higher edge than the best bets at table games, partly because they pay for features, graphics, jackpot pools and licensed themes, and partly because their maths is invisible to the player. A European roulette wheel has 37 pockets and pays 35 to 1 on a single number, so the edge is 1 ÷ 37, or about 2.70%. The Wizard of Odds roulette guide (opens in a new tab) sets out the full bet-by-bet maths.

Comparing raw percentages can mislead, though. A slot spin takes a few seconds; a roulette spin can take a minute or more. A lower edge on a faster game can still cost more per hour. What matters for your budget is edge × stake × number of bets.

House edge on UK pub, arcade and casino machines

Land-based gaming machines in Great Britain must display their theoretical target return to player, which lets you work out the edge in the same way. The Gambling Commission’s guidance on gaming machine categories (opens in a new tab) requires this for Categories B1 to B4 and C, and for most Category D machines (crane grabs and penny falls are exempt). Crucially, it sets no minimum return. The percentage is chosen by the manufacturer and operator within the machine’s approved settings.

Operators of these machines pay Machine Games Duty on their net takings: 5% where the cost to play is 20p or less and the top prize £10 or less, 20% for other games costing up to £5, and 25% above that. That duty, along with rent, the machine supplier’s share and the venue’s profit, comes out of the house edge. Players pay no tax on winnings.

House edge vs hold: theory and what actually happens

In the trade, “hold” usually means what a machine actually kept over a period, while house edge is what it should keep in theory. Over a week a pub machine might take £1,000 in stakes. If its target return is 90%, the theoretical hold is £100, but the real figure might be £40 after a big payout or £180 after a quiet run. Over months and years the two converge.

For a single player the gap is far wider still. One session is a tiny sample, which is why someone can win on a game with a 5% edge and lose on one with a 2% edge. It describes the game, not your evening. Volatility, explained on our standard deviation page, tells you how wide the gap can be.

Slot bonuses and the house edge

Bonus wagering works by making you stake bonus money several times, and the edge applies each time. Since 19 January 2026, bonus wagering in Great Britain is capped at 10 times the bonus, which makes the maths more manageable. On a £20 bonus with 10x wagering you must stake £200; at a 4% edge the average cost of that play is £8, so on average you would keep about £12 of the bonus value, before any game or stake restrictions. The wagering cap for slot bonuses page explains the rule.

No-wagering free spins work differently: you don’t stake your own money on them, and winnings are paid as cash. The edge still shapes what they are worth. 100 spins at 10p on a 96% game are worth about £9.60 on average, though actual results vary widely.

How to check a slot machine’s house edge

1. Online, open the game’s help or paytable screen and find the RTP percentage.
2. If the screen shows more than one figure (for example with and without a feature), note the one that applies to how you play.
3. Subtract the RTP from 100% to get the house edge.
4. Multiply your planned total stake (stake × spins) by the edge to get the average cost.
5. On a pub or arcade machine, read the target percentage shown on the machine or its information screen and do the same sum.

Our guide to reading slot RTP in the UK shows where the figure appears on different games and what to do if you can’t find it.

House edge myths and facts

• “A betting system can overcome the edge.” Raising or lowering stakes after wins or losses doesn’t change the percentage kept on each pound. The percentage is fixed by the paytable, not by how you bet.
• “Max bet improves the edge.” On almost all modern slots RTP is the same at every stake. A few older-style games are exceptions and say so in the rules.
• “The edge is lower late at night.” Online games in Great Britain can’t change their odds during play, and land-based machines don’t switch percentages by time of day.
• “A machine that has just paid out has a bigger edge now.” On random games each spin is independent. Compensated fruit machines are the exception that proves the rule, and they still keep their target percentage overall.

Where to play UK slots with published RTP

All three partner casinos below are licensed by the Gambling Commission, so each slot must show its RTP before you play and you can work out the house edge yourself. Their welcome offers are for new customers aged 18+ and terms apply. PlayOJO’s offer is 80 free spins on Big Bass Bonanza at 10p each after a first deposit of £10 or more, with winnings paid as cash and no wagering. At Coral, depositing and betting £10 on slots brings 100 free spins at 10p on selected games, valid for 7 days, with no wagering on winnings. At Ladbrokes, playing £10 on slots brings 50 free spins a day for 10 days, up to 500 in total at 10p each, with no wagering.

Game libraries and RTP versions vary by casino and change over time, so search the lobby and open the help screen of any game you choose. Losses are the likely outcome over time, so play only with money you can afford to spend. Free, confidential help is available from the National Gambling Helpline on 0808 8020 133 and through NHS gambling support (opens in a new tab).

18+. Gambling should be entertainment that costs money, not a way to make it. Decide a budget before you play: plan a slot budget. Free, confidential help: National Gambling Helpline 0808 8020 133.