The arithmetic
What is the house edge in gambling?
House edge is the built-in margin that makes a gambling business a business. It ranges from under 1% on the best table bets to well over 20% on the worst side bets and lottery-style games.
Same word, wildly different numbers, which is why quoting it without naming the bet is meaningless.
The spread, cheapest to worst
Blackjack on a chart, roughly 0.5%. Baccarat banker, 1.06%. Craps pass line, 1.41%. Single-zero roulette, 2.70%. Double-zero roulette, 5.26%.
Slots typically 3% to 6%. Bingo depends entirely on the room's prize share. Keno runs 20% to 30%. Casino side bets sit between 5% and 15% almost without exception.
The pattern is consistent: the more a bet pays when it lands, the more it costs while it does not.
Edge versus hold
House edge is per bet. Hold is what the operator actually keeps at the end of a session, and it is much larger because money gets staked repeatedly.
A C$100 deposit put through a 4% game twenty times over is C$2,000 of turnover and C$80 of expected cost. The edge was 4%. The hold on your deposit was 80%.
Sportsbook margins
The equivalent number in a sportsbook is the overround. Add the implied probabilities of every outcome and the amount over 100% is the margin.
Across the books we track it runs from a little under 4% on headline two-way markets to several times that on props and long parlays. Unlike a casino edge, you can shop it, which is worth more than any promotion.