KEY TAKEAWAYS
The house edge is the average share of every wager that a casino keeps over the long run. If a game has a 5% house edge, the house keeps about $5 of every $100 that players wager, on average. It is the reason casinos stay in business even though some players win on any given night. The house edge does not predict what happens in one session. A player can win big on one visit and lose on the next, but across millions of bets the average settles close to the edge. That is why understanding it matters before risking any money: it is the price tag of the entertainment. This guide explains the house edge in plain words, shows where it comes from, walks through a hypothetical example with every step of the math, compares the edge in common games, and clears up the beginner misconceptions that cause the most confusion. It stays at overview level and does not teach the rules of any single game. To see the bigger picture of how gambling businesses earn money, start with what gambling is and how it works.
What the House Edge Means
The house edge is the casino’s average profit expressed as a percentage of the money wagered. It is also called the house advantage. A 2.70% edge means that, on average, the casino keeps $2.70 for every $100 wagered by players.
The word wagered matters. It counts every bet placed, not only the money a player brought. A player who bets $10 fifty times has wagered $500, even if the same $50 was won, lost and rebet along the way. The edge applies to the total wagered, which is why fast games cost more per hour.
The house edge is a long-run average, not a promise about one session. A single bet either wins or loses; it never loses 2.70%. Only across a very large number of bets does the average settle close to that number, which is the same idea behind a fair coin landing heads half the time over thousands of flips but not necessarily in ten.
The edge has a mirror image called the return to player, or RTP, mostly used for slots. RTP is the share of wagers a game pays back on average, so the house edge equals 100% minus the RTP. A hypothetical slot with a 95% RTP has a 5% house edge.
Where the House Edge Comes From
The edge comes from paying less than the true odds. True odds describe how often something really happens; payout odds describe what the casino pays when it does. The gap between the two is the casino’s margin, and it is built into the rules of the game. For the difference between odds and chance, see odds vs. probability.
A roulette example
A European roulette wheel has 37 pockets: the numbers 1 to 36 and a single zero. A bet on one number wins in 1 pocket and loses in 36, so the true odds are 36 to 1 against. The casino pays only 35 to 1. If a player bets $1 on one number 37 times, the average outcome is one win of $35 and 36 losses of $1, a net of −$1, which is −1/37 or about 2.70% of the wagers.
An American wheel adds a second zero, so there are 38 pockets and the true odds are 37 to 1 against, while the payout stays 35 to 1. The average result over 38 bets is $35 won against 37 lost, a net of −$2, which is −2/38 or about 5.26% house edge. The extra zero roughly doubles the cost.
Other ways the edge is built in
Other games build in the edge differently. Sportsbooks charge a fee, called the vig, by offering prices such as −110 on both sides, and poker rooms take a fee called the rake. Slot machines are set to return less than they take in. The method differs, but the effect is the same: the house earns a small, steady share of the action.
A Simple Example With Real Math
Suppose a hypothetical player makes 40 spins on a roulette wheel, betting $5 on a single number each time, so $200 is wagered in total. The expected loss is the amount wagered times the house edge.
On a European wheel, 2.70% of $200 is about $5.40. On an American wheel, 5.26% of $200 is about $10.53. These are averages, so the actual result of any one session can be far better or far worse.
Here is why. Suppose the player hits the number once in the 40 spins on the European wheel. The win pays 35 to 1, which is $175 profit on a $5 bet. The other 39 spins lose $5 each, or $195. The net result is −$20, so one lucky hit still leaves the player behind. A second hit would leave the player ahead by $160.
Sessions like this split into three groups. In about 33% of them the player never hits and loses all $200. In about 37% there is exactly one hit and a $20 loss. In about 29% there are two or more hits and the player finishes ahead. Roughly three in ten sessions end in profit, yet the average across all of them is still a loss of about $5.40.
The edge predicts the average over many players and many sessions. It does not say which player will win. Treat the expected loss as the price of the entertainment, and decide in advance whether that price is worth paying.
How the House Edge Compares Across Games
The edge differs a lot from game to game and often depends on the rules or on the specific bet. The table shows common reference values and what each costs per $100 wagered. The same casino can offer a very cheap bet and a very expensive one in the same game.
| Game or bet | House edge | Average cost per $100 wagered |
|---|---|---|
| Blackjack, 3:2 table, perfect basic strategy | About 0.5% | About $0.50 |
| Blackjack, 6:5 table | About 1.9% (roughly 1.4 points higher) | About $1.90 |
| Craps, Don’t Pass | 1.36% | $1.36 |
| Craps, Pass Line | 1.41% | $1.41 |
| Baccarat, Banker (8 decks, 5% commission) | 1.06% | $1.06 |
| Baccarat, Player (8 decks) | 1.24% | $1.24 |
| Baccarat, Tie (pays 8 to 1) | 14.36% | $14.36 |
| European roulette (single zero) | 2.70% | $2.70 |
| American roulette (double zero) | 5.26% | $5.26 |
| Sports bet at −110 on both sides | About 4.55% hold | About $4.55 |
| Slots | 100% minus RTP; varies by game | Varies; verify for any real game |
These figures assume specific rules, and rules differ between casinos, so the edge at a real table may be higher or lower. Blackjack shows how sensitive the number is: the same game costs about four times as much at a 6:5 table as at a 3:2 table. Poker has no house edge at all because players compete against each other; the room takes a rake instead.
A lower edge is cheaper but never free. Even the lowest figures in the table are above zero, which means the average player loses over time. Games with a low edge can still feel expensive if they are played quickly, because more money is wagered per hour.
Common Beginner Misconceptions
“A 5% edge means losing 5% of your money each visit” is a common mistake. The edge applies to the total wagered, not the money brought, and it is an average. A player may win the visit, lose it all, or finish near the middle.
“The house wins every bet.” It does not. Players win many bets and many sessions. The edge simply means the average result over a very large number of bets favors the house.
“A hot streak means the edge has gone away.” Each spin or hand is independent of the last, and no streak changes the edge. A run of wins is luck, and the average still pulls toward the house over time.
“A betting system can beat the edge.” Raising or lowering bets changes how much is at risk, not the percentage the house keeps from each dollar wagered. No system changes the house edge.
First Steps: Using the House Edge Wisely
Before playing, look up the rules and the edge of the specific game, because paytables and table rules change the number. Compare similar games, and choose the lower-cost bet where there is a choice. Ask for the house rules if they are not posted.
Then work out a rough cost for the session. Multiply how much you expect to wager by the edge, and decide whether that price fits your entertainment budget. Set a limit on money and time, never gamble with money needed for essentials, and never raise bets to chase a loss. Legal age and rules vary by state and venue, so check where you are. The practical side of placing a bet is covered in how to place your first bet.
Where to Go Next
To see how skill can shrink the edge in some games but not others, read luck vs. skill in gambling. For how a sportsbook builds its fee into prices, see how sports betting works. Knowing the edge is the first step to knowing the real cost of any bet.
