House edge is the percentage of all stakes a game is mathematically set to keep over the long run: 100% minus its return to player. A slot paying back 96% of stakes carries a house edge of 4%.
How the house edge works in practice
The edge applies to turnover, not to deposits. European roulette's single zero sets the margin at 2.7%: 1,000,000 staked in a month keeps an expected gross of 27,000. Single nights land somewhere else, but over enough rounds the realised win converges on the theoretical one, so operators read margins monthly rather than nightly.
Blackjack sits at the other end: at roughly 0.5% under correct basic strategy it needs about five times the turnover for the same gross. Low margin games pay through volume, high margin games through rate.
What the house edge means for an operator
Three consequences follow. First, forecasting: expected gross gaming revenue is turnover weighted by the margin of each title, so the game mix is a commercial decision. Second, configuration: many slots ship with several certified RTP settings, and choosing one fixes your margin and the player's experience together. Third, downstream economics: gross is the starting line for bonus cost, fees, tax and royalties, the deductions walked through in our worked example of GGR and NGR.
Related terms
- RTP The same number from the player's side: what a game pays back.
- The RNG behind every round The certified generator making each outcome independent, so a theoretical margin becomes a realised one over volume.
- The gambling platform recording every stake The system of record where theoretical and realised margins get reconciled.
Frequently asked questions
What does a 2% house edge mean?
Out of every 100 staked, the game returns about 98 and keeps 2, on average, over a very large number of rounds. It applies to turnover, not deposits: the same 100 can be staked repeatedly before the expected 2 is collected, so single sessions swing while monthly averages hold.
Is house edge the same as RTP?
Two readings of one number. Return to player states what a game pays back, the edge states what it keeps, and together they total 100%. A 96% RTP title and a 4% margin title are the same product described from opposite ends.
Can an operator change the margin of a game?
Only inside the configurations the studio built and certified. Many slots ship with several approved RTP versions, and the operator selects one per market, disclosing it where the regulator requires. Anything beyond those versions changes the tested build and requires re-certification.
Which games carry the highest margins?
Slots and novelty side bets sit at the top end, roulette in the middle, and blackjack or baccarat at the low end under correct strategy. Exact figures vary by title and RTP version, so check the game sheet, not the category, when assembling a lobby.
From margin theory to a running business
A margin earns money only inside a system that settles stakes and wins at scale and reports the result title by title. That reconciliation is the daily job of the casino software your lobby runs on. The rest of the vocabulary sits in the full iGaming glossary.