House edge,
computed.
Set the rules of any blackjack table — decks, soft 17, DAS, surrender, doubling restrictions, blackjack payout — and the calculator returns the house edge with perfect basic strategy. Then plug in your bet size and session length to see the expected loss and the variance you should expect to ride.
With perfect basic strategy. Every cell of the chart played right; every double, split, and surrender taken when the chart says to.
Open strategy chart for these rules →Variance approximation. Per-hand standard deviation in blackjack is ~1.15× the bet size (Schlesinger / Wong). At short hand counts, variance dominates expected loss — sessions can come back $50 ahead or $200 behind from variance alone. The expected loss only reliably surfaces over thousands of hands.
How the calculator computes the edge
The calculator composes documented per-rule deltas vs a 6-deck S17 DAS late-surrender 3:2 baseline (~0.41% house edge). Each toggle adds or subtracts a published value:
Deck count: 1d -0.48% 2d -0.18% 4d -0.02%
6d 0.00% 8d +0.02%
Soft 17: Hits +0.20%
Double after split:Disallowed +0.14%
Surrender: None +0.08%
Re-split aces: Allowed -0.07%
Doubling: 9-11 only +0.13%
10-11 only +0.21%
Blackjack payout: 6:5 +1.39%These deltas are well-published and consistent across authoritative sources (Wizard of Odds, Edward Thorp's "Beat the Dealer", Stanford Wong's "Professional Blackjack"). The calculator is a UI on top of the math, not a simulator — what you see is the actual house edge under the rule set you select.
Why you can lose more than the edge says
The expected loss after N hands at bet size B with house edge p% is N × B × p%. That's a long-run average — over thousands of hands, that's where you'll land. But over a single session of 50, 100, or 200 hands, variance often dominates.
Per-hand standard deviation in blackjack is roughly 1.15 × B (Schlesinger's figure, Wong's figure lands at ~1.13). Over N hands, total session standard deviation grows as 1.15 × B × √N. That's the "one-sigma swing" figure in the calculator — about 68% of sessions land within that range of expected.
The "edge dominates noise after" figure is a rough threshold for when expected loss exceeds one-sigma swing. Below that hand count, your session outcome is mostly variance; above it, the edge consistently surfaces.
Practical implication: a 100-hand session at $25 on a 0.41% edge has expected loss of ~$10 and a one-sigma swing of ~$290. Those numbers describe almost every blackjack session anyone has ever played — wins and losses dominate the variance long before the edge consistently surfaces.
Use the result
Once you've set your rules, open the chart for this exact variant. Hover any cell for the EV.
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