Lay Bet House Edge

Lay-bet house edge in craps is not created by the probability of seven beating the chosen number. The true-odds relationship already prices that probability fairly. The casino edge appears when a commission, usually called the vig or vigorish, is added to the transaction. That makes lay bets a useful lesson in a point many players miss: a wager can win more often than it loses and still have negative expected value.

A lay bet is made against 4, 5, 6, 8, 9, or 10. The bet wins if 7 appears before the selected number and loses if the selected number appears first. Non-resolving rolls simply continue the wager.

For table procedure first, read Lay Bets Explained. This page concentrates on the pricing: true odds, commission timing, rounding, risk-to-win ratios, and the denominator used when someone quotes a “house edge.”

The probability side of a lay bet is straightforward

Once a lay bet is working, only two totals resolve it: 7 or the number being laid.

Those risk-to-win ratios are not a house advantage. They are the fair price for betting on the more likely resolving result.

For example, laying 10 at true odds can mean risking $40 to win $20. Seven has six combinations and 10 has three. Seven therefore resolves the bet twice as often as 10, so the fair winning profit is half the amount at risk.

Without commission:

Probability of win = 6 / 9 = 2/3
Probability of loss = 3 / 9 = 1/3

EV = (2/3 × $20) - (1/3 × $40)
EV = $13.333... - $13.333... = $0

The lay bet becomes a casino-edge wager only when the vig is introduced.

Commission timing changes the effective edge

This is the part that makes one universal “lay bet house edge” misleading.

A casino can have rules about:

• what amount the commission is calculated from;
• whether commission is collected when the wager is made or only when it wins;
• minimum commission increments;
• rounding up or down;
• minimum lay amount needed for clean payouts;
• whether a particular table offers the same treatment on every lay number.

New Jersey’s regulated craps rules, for example, permit true-odds lay bets and expressly allow the casino’s rules to determine whether the percentage is collected when the wager is made or only when it wins. The regulated payout ratios shown for lay bets are 1-to-2 on 4/10, 2-to-3 on 5/9, and 5-to-6 on 6/8. That is a useful reminder that the posted house procedure controls the real cost, not a generic internet percentage.

The biggest practical distinction is whether the vig is paid on every wager or only after a win.

Worked comparison: lay 10 to win $20

Assume a simplified house rule in which the commission is $1 on a lay that wins $20. The example is deliberately explicit so the calculation can be checked; another casino may calculate or round its vig differently.

If the $1 commission is collected only on wins

The player risks $40. A winning resolution returns the $40 stake and produces $19 net profit after the $1 vig. A losing resolution costs $40.

EV = (2/3 × $19) - (1/3 × $40)
EV = $12.6667 - $13.3333
EV = -$0.6667 per resolving bet

Measured against the $40 amount at risk:

House edge ≈ $0.6667 / $40 = 1.67%

If the same $1 commission is paid regardless of outcome

True odds still balance the win and loss before commission. The fixed $1 cost now applies to every wager.

If $40 is treated as the betting risk and the commission is a separate fee, expected cost is $1 per resolved wager. Quoting the percentage requires the denominator to be stated. Against $40 of risk, that is 2.5%; against $41 actually put forward, it is about 2.44%.

That denominator issue is why two sources can publish different-looking percentages while describing economically similar action.

The same $1 vig behaves differently on 5, 6, 8, and 9

Suppose, again only for comparison, that each bet is sized to win $20 and a $1 vig is charged only on winning bets.

The 4/10 bet requires the most money at risk to win the same $20, so the same $1 winning commission is a smaller percentage of the amount laid. The 6/8 bet puts less capital at risk for the same $20 target, so the $1 commission consumes a larger percentage of that risk amount.

If the casino collects the commission upfront instead, the pattern changes again because the fee is paid on losing resolutions too.

The correct comparison therefore needs four facts: number laid, risk amount, win amount, and exact commission rule.

Rounding can matter more than the headline percentage

Commission is often handled in practical chip increments. That means a theoretically “5%” vig may not equal exactly 5% on a small wager.

Suppose the rule produces a minimum $1 commission. A player laying a small amount may pay $1 even when an exact percentage calculation would have been less than $1. On a much larger wager, the same rounding increment becomes less important.

This creates a common trap: a player reads that a lay bet has a certain theoretical edge, then places a small wager whose rounded commission makes the effective cost higher.

A better calculation is:

Effective Commission Rate = Actual Commission Charged / Reference Amount Used by House

Then use the actual commission in the expected-value formula rather than assuming an idealized percentage.

Lay bets are not the same as laying odds behind Don’t Pass

Both positions bet against a point, so the language is easy to confuse.

A lay bet on a number is a standalone wager against 4, 5, 6, 8, 9, or 10 and normally carries its own commission structure.

Laying odds behind Don’t Pass or Don’t Come is an additional odds wager attached to an existing contract bet. The odds portion is normally paid at true odds and is conceptually different from a standalone lay bet.

That distinction matters when comparing house edge. A player cannot take the edge quoted for a Don’t Pass line plus free odds and apply it to a standalone lay-number bet. The bets have different structures, different capital at risk, and different commission treatment.

Use Craps Odds for the line-bet odds side and Craps House Edge for the broader comparison.

A high hit rate can hide an awkward loss profile

Lay 4 and lay 10 resolve in the player’s favor two-thirds of the time. That sounds comfortable until the payoff structure is remembered: the player may risk $40 to earn about $20 before commission.

A short sequence can therefore look like this:

Win +$19
Win +$19
Loss -$40
Net = -$2

The player won two of three resolved bets and still lost money in this example.

That is not evidence of unusual luck. It is exactly what the risk-to-win structure permits. The hit rate describes how often the wager wins; expected value describes what those wins and losses are worth together.

This is especially important for players who use lay bets because they want to “be with the seven” or because frequent small wins feel safer. Probability of winning a resolution is only one part of risk.

Multiple lay bets change exposure, not the mathematics of each number

A player can lay more than one number at the same time. For example, laying both 4 and 10 means a seven can win both active bets, while either 4 or 10 can knock down its corresponding lay.

That does not create a new favorable system. It creates a portfolio of correlated craps bets. Seven is beneficial to several positions simultaneously, but each wager still carries its own true-odds relationship and commission.

Total expected cost is the sum of the expected costs of the active bets, adjusted for the exact house rules and time they remain working.

Total Expected Loss ≈ Sum of Expected Losses on All Active Lay Bets

The important operational consequence is capital exposure. A player who spreads several lay bets may have much more money on the layout than the small target wins make obvious.

Dealer procedure matters because risk and win amounts differ

Lay bets are more error-prone than a simple even-money wager because the amount sitting on the layout is not the amount the player expects to win.

A clean settlement requires the dealer to know:

• which number is being laid;
• whether the bet is correctly marked as lay action;
• the amount risked;
• the true-odds win amount;
• the commission and when it is collected;
• any rounding rule;
• whether the wager was working on that roll.

A player can also misread the outcome. When the laid number rolls, that lay loses; when seven rolls first, it wins. Clear dealer calls and correct bet placement reduce disputes.

From a surveillance or floor perspective, the protection issue is not that lay bets are inherently suspicious. It is that unusual risk-to-win ratios, late calls, commission handling and less-frequent wager types create more room for settlement mistakes if the crew is weak or rushed.

House edge should always name its denominator

There are at least three quantities someone might divide expected loss by:

1. the amount physically risked on the lay bet;
2. the amount the player is trying to win;
3. the total cash committed including a separately collected commission.

Those denominators produce different percentages.

For meaningful comparison, use the same basis every time. On ChipsAndTruths, the safest way to read a lay-bet example is to look at the stated dollars as well as the percentage. If an article says a wager has an expected loss of $0.67 while risking $40, there is no ambiguity about the economic effect.

The general formula is:

Player EV = (P(win) × Net Win) - (P(loss) × Amount Lost) - Any Unconditional Fee

House Edge on Risk = -Player EV / Amount Risked

If commission is charged only on wins, put it inside Net Win. If it is charged regardless of outcome, treat it as an unconditional fee. If the casino uses a different calculation base or rounding rule, substitute the actual numbers.

What to check before comparing one lay table with another

Before deciding that one lay bet is “better” than another, verify:

• Is vig charged upfront or only on wins?
• What amount is the vig calculated from?
• What is the minimum commission?
• How is the commission rounded?
• What bet multiples produce clean payouts?
• Can the wager be reduced or removed before the dice are out?
• Are the rules the same on electronic or automated craps?

Only then does a quoted edge become useful.

The durable truth is simple: true odds make the underlying lay proposition fair; the commission makes it a house-edge wager. Winning more than half of the resolving bets does not change that.

Continue with Buy Bet House Edge to see the opposite side of the same pricing idea, Place Bet House Edge for built-in payout disadvantage, and the Craps Odds Calculator when you want the dollar relationships instead of a memorized percentage.