Every casino game returns less than it takes. That is not a scandal, it is the design: the gap between what a game pays back and what it takes in is the house edge, and it is the price of playing. The expected outcome of gambling is a loss, and the longer you play the more reliably that expectation shows up in your balance.
What almost nobody does is convert that price into pounds per hour — the only form in which it becomes a decision you can actually weigh. So that is the first thing on this site.
The formula, in one line
expected loss = total staked × (1 − RTP)
The number that trips people up is total staked. It is not the money you put into your account. It is every pound that passes through the game, winnings included, because a win you re-stake gets charged the house edge again. A £20 deposit played at 20p a spin will routinely stake several hundred pounds before it is gone, and the edge is levied on that several hundred, not on the £20.
That single distinction explains most of what feels inexplicable about slot sessions. You did not lose £20 to a 4% house edge. You lost £20 to a 4% house edge applied roughly twenty-five times over, because the same money went round and round.
Speed matters more than house edge
Two games, two edges, two very different bills:
| Game | House edge | Rounds per hour | Stake | Expected loss per hour |
|---|---|---|---|---|
| Slot at 96% RTP | 4.00% | 600 | £0.20 | £4.80 |
| Slot at 92% RTP | 8.00% | 600 | £0.20 | £9.60 |
| European roulette | 2.70% | 45 | £5.00 | £6.08 |
| Slot at 96% RTP | 4.00% | 600 | £1.00 | £24.00 |
The roulette wheel has the lowest edge on the list and is not the cheapest row, because a mobile slot deals you a hand every few seconds and a table does not. Decisions per hour is the multiplier nobody looks at. If you want to spend less, slowing down does more than chasing a slightly better RTP figure.
This is also why Great Britain's 2021 online rules went after mechanics rather than maths: a minimum spin duration of 2.5 seconds, no autoplay, no turbo or slam-stop, and no playing several slots at once. None of those change a game's RTP by a single point. All of them change how much money passes through it in an evening.
Start here
Expected loss calculator
The full version, with per-game presets and your session cost as a share of what you brought.
Bonus wagering calculator
Turn a wagering requirement into the turnover it demands and the expected loss that turnover costs. Usually more than the bonus.
House edge and RTP by game
What the figures are, where they come from, and why the same slot can ship at three different RTPs.
Variance: why RTP says nothing about tonight
Long-run averages, short-run reality, and the dry-run probability tool.
Licensing and player protection
What a UKGC or MGA licence obliges an operator to do, and how to check one yourself.
Deposit limits, time-outs and self-exclusion
Every control that exists, what each one actually blocks, and where free help is.
What this site does not do
It does not review casinos, score them, rank them or list them. It carries no affiliate links and no advertising, and it is not paid by anybody in the industry. That is a deliberate choice rather than a boast: the moment a site earns money per player sent, its incentive is to make gambling look like a good idea, and the maths on this site says plainly that it is not one.
There is nothing here that will help you win. The house edge is not a difficulty setting to be outplayed — it is a fixed toll on turnover, and no staking pattern, session length or "strategy" alters it. What the maths can do is tell you the price in advance, so that if you choose to pay it you are choosing knowingly.
18+. Gambling has a negative expected value; treat any money staked as spent. If it has stopped being a choice, free confidential support is available from GamCare on 0808 8020 133, 24 hours a day, and from BeGambleAware.