Buy and Lay bets: paying commission
Chapter 3: More ways to bet · Lesson 10 of 21 · 7 min read
Buy bets pay true odds minus a commission, and Lay bets are the Don't-side version. Learn when Buy beats Place.
Buy bets are like place bets, except the casino pays true odds (2:1 on 4/10, 3:2 on 5/9, 6:5 on 6/8) and charges a 5% commission, called the vig. In this app, as at many Las Vegas casinos, the vig is 5% of your bet, rounded down to whole dollars (minimum $1), and taken only when you win.
That rounding is why you should buy for $20 or more. At $20 to $39 the vig is $1, so the $1 vig is exactly 5% of a $20 buy. Buy for less and the $1 minimum takes a bigger bite: a $10 buy on the 4 costs 3.33% instead of 1.67%. Buy a bit more than $20 and the vig stays at $1: a $25 buy on the 4 costs just 1.33%.
| Buy (for $20) | House edge (vig on win) | Compare Place |
|---|---|---|
| 4 / 10 | 1.67% | 6.67% → buy these instead |
| 5 / 9 | 2.00% | 4.00% → buying is cheaper, if you buy $20 or more |
| 6 / 8 | 2.27% | 1.52% → place these instead |
So the rule of thumb is: place the 6 and 8, buy the 4 and 10 (and buy the 5 and 9 if you really want them). A Buy 4 wins +$40 less the $1 vig, so you collect $39; a Buy 5 or 9 for $20 wins $30 less $1 = $29; a Buy 6 or 8 for $20 wins $24 less $1 = $23. For 5/9 and 6/8, full-pay units are $2 and $5, so $20 works everywhere.
Some casinos take the vig up front, when you make the bet. The edge is then measured against your bet plus the vig, and every buy bet costs 4.76%: still better than placing the 4/10, but no longer cheap.
Lay bets are the reverse: you bet that 7 comes before the number. 7 is more likely, so you have to risk more than you win. You pay true odds the other way (lay $2 to win $1 against 4/10, $3 to win $2 against 5/9, $6 to win $5 against 6/8), and the vig is 5% of what you win, rounded down to whole dollars with a $1 minimum. To make that $1 vig worth it, lay in the efficient amounts: $40 against the 4 or 10, $30 against the 5 or 9, and $24 against the 6 or 8. Each of those wins $20, less a $1 vig, so you collect $19.
| Lay | House edge (vig on win) | Vig paid up front |
|---|---|---|
| 4 / 10 (lay $40) | 1.67% | 2.44% |
| 5 / 9 (lay $30) | 2.00% | 3.23% |
| 6 / 8 (lay $24) | 2.27% | 4.00% |
Lay bets are always working, including on the come-out, and you can take them down at any time. Taking a bet down doesn't cost any vig.
If you want to bet against numbers, a Don't Come bet with lay odds is cheaper still (lesson 11).
Show the math: Buy and Lay edges
Vig is 5% of the bet on a win, rounded down to whole dollars (minimum $1). Buy 4, $20: win (1/3) pays 40 − 1 = 39; lose (2/3) −20. EV = 13 − 13.33 = −0.333 → −0.333/20 = 1.667% (1/60). Buy 5, $20: (2/5)(30 − 1) − (3/5)(20) = 11.6 − 12 = −0.4 → 2.00% (1/50). Buy 6, $20: (5/11)(24 − 1) − (6/11)(20) = −5/11 → 2.27% (1/44). Buy 4, $25: (1/3)(50 − 1) − (2/3)(25) = −1/3 → 0.333/25 = 1.33%. Buy 4, $10: (1/3)(20 − 1) − (2/3)(10) = −1/3 → 3.33%. Vig up front: you risk $20 + $1 = $21 on an otherwise fair bet and expect to lose the $1 vig: 1/21 = 4.76%.
Lay 4, $40, wins $20 with P = 2/3, vig $1 on the win: (2/3)(19) − (1/3)(40) = −2/3 → 0.667/40 = 1.667% (1/60). Lay 5, $30, wins $20 with P = 3/5: (3/5)(19) − (2/5)(30) = −0.6 → 2.00% (1/50). Lay 6, $24, wins $20 with P = 6/11: (6/11)(19) − (5/11)(24) = −6/11 → 2.27% (1/44). Up front: the vig is $1 on top of the lay, so the edge is 1/(lay + vig) = 1/41 = 2.44% (4/10), 1/31 = 3.23% (5/9), 1/25 = 4.00% (6/8).
Buy the 10
Interactive practice table. Try this in the app (free, play money).
Lay the 4
Interactive practice table. Try this in the app (free, play money).
You want to bet on the 10. What's the cheapest way (vig on win, $20 bet)?
- Place 10 (6.67%)
- Buy 10 (1.67%)
- Hard 10
- Big 6
Show answer
B: Buy 10 (1.67%). Buying the 4 and 10 cuts the edge from 6.67% to 1.67%.
You want to bet on the 6. Which is cheaper?
- Place 6
- Buy 6
- They're equal
- Big 6
Show answer
A: Place 6. Place 6 is 1.52%; Buy 6 is 2.27%; Big 6 is 9.09%.
Why buy for $20 or more?
- Table minimum
- The vig rounds down to whole dollars with a $1 minimum, so small buys pay a bigger share
- Buy bets pay more above $20
- The dealer asks for it
Show answer
B: The vig rounds down to whole dollars with a $1 minimum, so small buys pay a bigger share. $20 x 5% = $1. At $10 the $1 minimum vig makes a Buy 4 cost 3.33% instead of 1.67%.
A $30 Lay bet against the 9 wins. What do you collect (vig 5% of the win)?
- $20
- $19
- $30
- $45
Show answer
B: $19. Lay 3 to win 2: $30 wins $20, less a $1 vig = $19 (you also keep your $30).
If the vig on a Buy bet is paid up front, the edge on every number is...
- 1.67%
- 4.76%
- 5%
- 0%
Show answer
B: 4.76%. You pay $1 on a $20 bet, so you risk $21 to lose $1 on average: 1/21 = 4.76%.