House edge and RTP are the same fact stated from opposite ends. RTP — return to player — is the share of everything staked that a game pays back over an enormous number of rounds. The house edge is what is left.
house edge = 100% − RTP
A 96% slot has a 4% edge. European roulette's 2.70% edge is a 97.30% RTP. The casino industry prefers RTP for slots and house edge for table games, which makes the two look like different concepts when they are one number written twice.
Where the table-game numbers come from
Table-game edges are not policy decisions. They fall out of the geometry of the game, which is why they are stable across every casino on earth.
European roulette has 37 pockets and pays a straight-up winner 35 to 1. Stake £1 on a number: you win £35 once every 37 spins and lose £1 the other 36 times, for an average of −£1 per 37 staked, or 1/37 = 2.70%. Every other bet on a single-zero wheel — red, dozens, splits, corners — produces exactly the same 2.70%, because the payouts are all scaled from the same 36-versus-37 mismatch.
Add a second zero and there are 38 pockets paying the same 35 to 1. The edge becomes 2/38 = 5.26%, nearly double, for a game that looks identical on screen. The one American bet that is worse still is the five-number line on 0, 00, 1, 2, 3, which pays 6 to 1 and carries a 7.89% edge.
| Game and bet | House edge | Equivalent RTP |
|---|---|---|
| Blackjack, common rules, basic strategy | around 0.5% | around 99.5% |
| Baccarat, banker (after 5% commission) | 1.06% | 98.94% |
| Baccarat, player | 1.24% | 98.76% |
| Craps, pass line | 1.41% | 98.59% |
| European roulette, any standard bet | 2.70% | 97.30% |
| American roulette, most bets | 5.26% | 94.74% |
| American roulette, five-number bet | 7.89% | 92.11% |
| Baccarat, tie paying 8 to 1 | around 14.4% | around 85.6% |
| Craps, any seven | 16.67% | 83.33% |
| Online slots, typical range | 4% to 8% | 92% to 96% |
Two entries deserve a footnote. Blackjack's figure assumes correct basic strategy and depends heavily on the rule set — the number of decks, whether the dealer stands on soft 17, whether you may double after splitting, and above all whether blackjack pays 3 to 2 or the far worse 6 to 5. A 6-to-5 table adds well over a point of edge on its own, which dwarfs every other rule variation combined. And the French variants of roulette that apply la partage or en prison refund or hold half of an even-money stake when zero lands, halving the edge on those bets to about 1.35% while leaving the rest of the table at 2.70%.
Slots do not have a natural edge
A slot's RTP is chosen, not derived. The designer builds a reel set and paytable, calculates the exact mathematical return, and submits it for testing. Nothing about the symbols on screen implies a return; the same visual game can be built to pay 96% or 92%.
That has a consequence which surprises a lot of regular players: the same slot title is frequently supplied to operators at more than one RTP setting, and the operator picks which to run. A game you have played for years at one site can be a materially worse game at another under an identical name and theme. The published figure in the game's information screen is the one that applies to the machine in front of you, and it is the only one worth entering into the expected loss calculator. Feature buys, where offered, are frequently priced with their own return figure that differs from the base game's.
Slot RTP is also calculated over a colossal number of simulated spins — typically millions — because that is the only sample in which the figure is meaningful. Over one evening it is very nearly irrelevant, which is the subject of variance and session results.
What the edge is charged on
The most common misreading of RTP is to apply it to a deposit. A 96% game does not mean you keep 96% of your deposit; it means the game keeps 4% of everything staked, and the same money is staked repeatedly.
Take £100 through a 96% slot at £1 a spin. Every spin puts £1 through the game and is expected to cost 4p of it. The first hundred spins are expected to return £96, which you then re-stake, and the edge is charged on that too. The expected balance falls in a straight line against the number of spins:
expected balance = bankroll − (spins × stake × house edge)
At £1 a spin on a 4% edge that is 4p a spin, so a £100 bankroll is expected to buy about 2,500 spins — roughly £2,500 of total turnover to lose the original £100. After a thousand spins the expected balance is about £60, and the money has been through the game ten times over to get there. That recycling is the whole mechanism: you are buying a quantity of play, and RTP sets its price per spin.
What house edge is not
It is not a per-session outcome, and no game "owes" you a correction after a losing run. Each spin of a compliant RNG game is independent, so a slot that has taken money for an hour is exactly as likely to pay on the next spin as it was on the first. Progressive jackpots complicate the accounting slightly — part of every stake funds a pot that is eventually paid to somebody — but the edge on your own play is unaffected by how long the pot has been growing.
It is also not something a betting pattern can move. Doubling after a loss, flat staking, "due" numbers and stop-loss rules all rearrange the shape of your results without touching the average, because a fixed percentage of turnover is a fixed percentage of turnover however that turnover is distributed. The only inputs you genuinely control are stake size, speed and duration — which is why those are the three fields in the calculator, and why the honest summary of this entire page is that the cheapest game is the one you play less of.