The short answer
A “Lay” bet carries a house edge between 2.44% and 4.00%, depending on the number you are laying against and when the casino collects the commission.
The full calculation
A Lay bet is the opposite of a Buy bet; you are betting that a 7 will roll before the chosen number. You pay a 5% commission (“vig”) on the potential win amount to get paid True Odds.
Laying the 4 or 10 (Pays 1:2): If you lay $40 to win $20, and the vig is $1 (5% of $20): $HE = rac{1}{40 + 1} pprox 2.44%$
Laying the 6 or 8 (Pays 5:6): If you lay $30 to win $25, and the vig is $1: $HE = rac{1}{30 + 1} pprox 3.23%$ (Some houses push this to 4.00% depending on win calculation).
What this means at the table
Laying the 4 or 10 is a solid defensive play if you think a shooter is about to “Seven Out.” A 2.44% edge is better than roulette and significantly better than any bet in the center of the table. However, you are risking a large amount of money to win a small amount ($50 to win $25), which can lead to rapid bankroll depletion if a shooter hits a few lucky outside numbers.
Common mistakes around this number
The “Upfront Vig.” Always ask the dealer: “Is the vig only on the win?” If they charge the 5% up front, the house edge nearly doubles. Also, never “Lay” the 6 or 8. A house edge of 3% to 4% is too high when you can simply play the Don’t Come or Don’t Pass for a much lower 1.36% edge.
See also
Compare this to the Craps House Edge Buy Bets or learn the Craps Dont Pass strategy.
In Detail
Lay bets feel powerful because you get the 7 on your side. Then the commission walks in and reminds you the casino read the same math book.
This page is about the cost of betting 7 before a number. On the surface, that may sound like one small corner of craps, but in a real casino it touches the three things that decide whether a player survives the table: the written rule, the payout, and the way the bet feels when chips are already in action. Craps is dangerous for beginners because a bet can feel smart, social, or lucky while still being badly priced.
The math that matters: Two dice create 36 equally likely ordered combinations. The shape of the game comes from that grid: 7 has 6 combinations, 6 and 8 have 5 each, 5 and 9 have 4 each, 4 and 10 have 3 each, 3 and 11 have 2 each, and 2 and 12 have only 1 each. True lay odds are 1:2 against 4/10, 2:3 against 5/9, and 5:6 against 6/8. The commission turns fair odds into negative expectation. Expected value is the grown-up way to price a bet: $EV=\sum(P_i\times W_i)-\sum(P_j\times L_j)$. If the payout is smaller than the true probability deserves, the difference is the house edge.
What it means on the felt: Lay bets can fit dark-side play, but they are not magic “seven is coming” buttons. A player who understands this subject does not need to act like a robot. You can still enjoy the noise, the shooter, the stick calls, and the little rush when the dice leave the hand. The point is to know when you are paying for entertainment and when you are making a lower-cost decision.
Casino-floor truth: Craps is built to move. The table crew wants clear bets, fast decisions, and clean payouts. The layout also nudges attention toward action. The safest-looking move is not always the cheapest move, and the loudest bet is almost never the best one. Good craps play is not about predicting the next roll. It is about refusing to overpay for it.
The mistake to avoid: Do not ignore vig and rounding. On lay bets, the commission is the bite. Also, never judge this topic by one lucky hit or one ugly loss. Short sessions are noisy. The math only shows its face over repeated decisions, which is exactly why casinos are patient and players are usually not.