Blackjack House Edge, Explained
Read this to turn a table's posted rules into a single number: the fraction of each bet you expect to lose over time, and the dollar cost of a session.
What the house edge means
The house edge is the average amount the casino keeps from each bet you make, expressed as a percentage of that bet. If a table has a house edge of 0.62% and you bet $25 a hand, you lose about 0.0062 \times 25 = 0.155 dollars per hand on average. Play 200 hands and the expected loss is roughly $31.
That number assumes you play perfect basic strategy: the mathematically correct hit, stand, double and split for every hand against every dealer upcard. Play worse than that and your real edge is larger. The calculator gives you the floor, the best you can do without counting cards.
Here is the hook. Two tables can look identical (same felt, same dealer, same $25 minimum) yet one costs you four times as much. The single line "Blackjack pays 6:5" instead of "3:2" swings the edge by about 1.4 percentage points. Everything else on the table combined moves it less.
When to use this estimate
Use it to compare tables before you sit down. When you walk a casino floor and see different rule placards, plug each set of rules in and pick the lowest number. Use it to size a session: multiply the edge by your total wagered to see the expected cost.
Do not use it as a prediction of one night. The edge is a long-run average. Over 200 hands your actual result swings widely around the expected loss because blackjack has high variance (blackjacks, doubles and splits all pay in multiples). The calculator's expected loss is the center of a wide bell, not a forecast.
The estimate assumes perfect basic strategy and flat betting. If you deviate from the chart, take insurance, or chase losses with bigger bets, your real cost rises. The number here is the best case for a non-counter.
The formula and the intuition
The calculator starts from a baseline edge for a common rule set, then adds or subtracts a published adjustment for each rule you change. The structure is additive:
Here E is the final house edge, E_0 is the baseline edge for the reference rules, and each a_i is the adjustment for one rule difference. A positive a_i helps the house; a negative one helps you.
The additive model works because each rule affects a different slice of hands, and the interactions are small. The table below lists the standard adjustments in percentage points. Negative means the rule lowers the house edge in your favor.
| Rule | Change from reference | Adjustment |
|---|---|---|
| Decks | 1 vs 6 decks | -0.48 |
| Decks | 2 vs 6 decks | -0.19 |
| Decks | 8 vs 6 decks | +0.02 |
| Dealer soft 17 | Hits (H17) vs Stands | +0.22 |
| Double after split | Not allowed | +0.14 |
| Doubling | 10 and 11 only | +0.09 |
| Late surrender | Offered | -0.08 |
| Blackjack payout | 6:5 vs 3:2 | +1.39 |
The reference set the calculator builds from is 6 decks, dealer stands on soft 17, double after split allowed, double on any two cards, no surrender, blackjack pays 3:2. That set has a baseline edge near 0.40%. Change any control and the matching row above shifts the number.
A worked example with the demo data
Six decks, H17, 3:2, $25 a hand
Use the demo settings: 6 decks, dealer hits soft 17, double after split allowed, double on any two cards, no surrender, 3:2 payout, $25 per hand, 200 hands.
- Start at the baseline for 6 decks with S17:
0.40%. - Dealer hits soft 17 instead of standing: add
+0.22. Running total0.62%. - Double after split is allowed, doubling is any two cards, no surrender, 3:2 payout: these all match the reference, so add
0.00. - Final house edge: E = 0.62\%.
- Expected loss per hand: 0.0062 \times 25 = 0.155 dollars.
- Expected loss over 200 hands: 0.155 \times 200 = 31 dollars.
So the honest cost of this session is about $31, on $5,000 total wagered (200 hands at $25). That is the number to expect on average. A single session can easily land $300 up or $300 down.
Reading and interpreting the result
Think in three layers. The edge is the rate. The expected loss is the rate times your total action. The spread is how far a real night wanders from that expected loss.
A useful rule of thumb for spread: over n hands of flat betting, the standard deviation of your net result is roughly 1.14 \times \sqrt{n} bet units. For 200 hands that is 1.14 \times \sqrt{200} \approx 16.1 units, or about $403 at $25 a hand. Your expected loss is only $31, so the swing dominates a single session.
This is why blackjack feels beatable in the short run. The $31 expected loss is buried inside a $400 swing. Over thousands of hands the swing grows like \sqrt{n} while the loss grows like n, and the edge wins.
Common mistakes
Three errors distort the number most often.
- Ignoring the payout
- Players fixate on decks and soft 17, then sit at a 6:5 table. That one rule adds
1.39points, more than a fresh single deck saves you. A 6:5 shoe with otherwise great rules is worse than a 3:2 shoe with poor rules. - Confusing edge with loss
- A
0.62%edge does not mean you lose 0.62% of your buy-in. You lose 0.62% of total wagered. If you replay the same $100 twenty times, you have wagered $2,000, and the expected loss is about$12.40, not $0.62. - Treating one session as the average
- The expected loss is a long-run center. Do not conclude the table is loose because you won one night, or rigged because you lost. The \sqrt{n} swing explains both.
Related tools
Blackjack has the lowest house edge of the common table games when you play it well. To see how it compares, check the Roulette Odds calculator, where even the best bet carries a 2.7% edge on a single-zero wheel, and the Craps Odds calculator, where the pass line sits near 1.41%.
To turn any edge into a dollar figure for a whole night, use the Expected Loss Calculator. For a game with a much larger edge and swing, the Slot Session Calculator shows how quickly expected loss piles up on machines.
Frequently asked questions
Why is a 6:5 blackjack payout so bad?
A natural blackjack happens about once every 21 hands, roughly 4.75% of the time. At 3:2 you win 1.5 units on it; at 6:5 you win only 1.2 units. That lost 0.3 units on 4.75% of hands works out to about 1.39% of every bet, which is why it outweighs every other rule.
Does fewer decks always help me?
Yes, for basic strategy. One deck instead of six lowers the edge by about 0.48 points, and two decks by about 0.19. Casinos usually offset this by pairing single-deck games with 6:5 payouts, which erases the benefit and then some.
How many hands until the edge shows up?
The expected loss grows with hands played while the swing grows with the square root. At 200 hands the swing (about $403 at $25) hides the $31 loss. At 10,000 hands the expected loss is $1,550 and the swing is about $2,850, so the loss becomes clearly visible but not yet dominant.
Is card counting included in these numbers?
No. The estimate assumes flat bets and perfect basic strategy. Counting changes your bet size with the count and can flip the edge in your favor, but that is a different model and not what this calculator computes.
The short version
Read the table's rules, add the adjustments, and you have your edge. Multiply by your total wagered for the honest cost. Above all, avoid 6:5 tables: no combination of good rules makes up for that single line. A 3:2 six-deck game with S17 costs about 0.40%, and even with H17 it stays near 0.62%, which remains one of the best deals on the casino floor.
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