Blackjack Strategy: What Actually Lowers the House Edge, Tested on 10M Hands
Quick answer
The best blackjack strategy is basic strategy: the mathematically best play for every hand against every dealer upcard. In our 10-million-hand simulation of a 6-deck game where the dealer stands on soft 17, it cut the house edge to about 0.47%. Choosing 3:2 tables, S17 and double after split matters as much; betting systems don't change the edge at all.
| Best strategy | Basic strategy (a fixed chart of plays) |
|---|---|
| House edge with it (6 decks, S17, DAS, 3:2) | about 0.47% in our simulation |
| Cost of a 6:5 table | about +1.36 percentage points |
| Cost of H17 | about +0.18 points in our simulation |
| Betting systems | Change swings, not the edge |
| Card counting | Only works in shoe games not reshuffled every hand |
There's one blackjack strategy that works on every hand: basic strategy. It's a fixed set of plays, worked out by computer, that gives the smallest possible house edge for a given set of rules. Our simulation dealt 10 million hands to a player following it in a 6-deck game where the dealer stands on soft 17. The house edge came out at about 0.47%.
This guide explains what basic strategy is, the rules worth memorising first, what table rules are worth, and why betting systems and hunches don't help.
What blackjack strategy can and can't do
Blackjack is unusual among casino games: your decisions change the odds. Hit a hand you should stand on, and the house edge grows. Play every hand the right way, and it shrinks to a fraction of a percent.
What strategy can't do is make the edge go away. Basic strategy minimises the cost of each hand, but the dealer still has one big advantage: if you bust, you lose, even if the dealer busts afterwards. A small edge means slow losses on average and plenty of winning sessions. It doesn't mean guaranteed profit.
Basic strategy: the rules to learn first
The full chart covers every hand, but most of its value comes from a handful of rules. Learn these first:
- Hard 17 or more: always stand.
- Hard 8 or less: always hit.
- Hard 12 to 16: stand against a dealer 2 to 6, hit against 7 to ace. Exception: hit 12 against a 2 or 3.
- Hard 11: double against everything except an ace. Hard 10: double against 2 to 9. Hard 9: double against 3 to 6.
- Always split aces and 8s. Never split 10s or 5s.
- Soft 17 or less (ace + 6 or lower): never stand. Hit, or double against the dealer's weak cards.
- Soft 18: stand against 2, 7 and 8; double against 3 to 6; hit against 9, 10 and ace.
- Soft 19 and 20: stand.
The logic behind them is simple. When the dealer shows 2 to 6, they're likely to bust, so you avoid taking risks. When the dealer shows 7 to ace, they're likely to finish with 17 or more, so you need to improve your hand.
Why the dealer's upcard matters so much
The dealer has no choices: they draw to 16 and stand on 17. That makes their chance of busting depend almost entirely on the upcard.
| Dealer upcard | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | A |
|---|---|---|---|---|---|---|---|---|---|---|
| Dealer busts | 35.4% | 37.4% | 39.4% | 41.6% | 42.3% | 26.2% | 24.5% | 22.8% | 23.0% | 16.7% |
We calculated these exactly for an infinite deck with the dealer standing on soft 17, after the dealer has checked for blackjack with a 10 or ace up. Notice the cliff between 6 and 7. Against 2 to 6, the dealer busts around 35% to 42% of the time, which is why you stand on stiff hands and double more. Against 7 or higher, they bust only about a quarter of the time or less.
The table matters as much as the play
Rules are part of strategy, because you choose the table. Here's what our simulation measured for a basic strategy player across four common rule sets:
| Rule set | House edge, blackjack pays 3:2 | House edge, blackjack pays 6:5 |
|---|---|---|
| 6 decks, S17, DAS | 0.47% | 1.83% |
| 6 decks, S17, no DAS | 0.53% | 1.89% |
| 6 decks, H17, DAS | 0.65% | 2.01% |
| 6 decks, H17, no DAS | 0.78% | 2.13% |
Three takeaways:
- 3:2 beats everything else. A 6:5 payout added about 1.36 points, nearly three times the whole edge of the best game. Our 6:5 blackjack guide goes into it.
- S17 beats H17. When the dealer hits soft 17, the edge rose by about 0.18 points.
- Double after split helps. Losing DAS cost 0.06 points in S17 games.
Insurance, side bets and surrender
Insurance is a side bet that the dealer has blackjack when showing an ace. It pays 2:1, so it needs a one-in-three chance to break even. In a 6-deck game where you hold no tens, 96 of the 311 unseen cards are tens: a 30.8% chance. That makes insurance lose about 7.4% of what you put on it, which is why basic strategy never takes it.
Side bets like Perfect Pairs or 21+3 usually carry much higher house edges than the main game. They're separate wagers, so basic strategy can't improve them.
Surrender, where offered, lets you give up half your bet before playing. Basic strategy uses it on a few hands, most often hard 16 against a 9, 10 or ace and hard 15 against a 10. The Wizard of Odds strategy pages in our sources show exactly where.
Do betting systems work in blackjack?
No. Martingale (double after every loss), Paroli (double after every win), 1-3-2-6 and the rest all change how much you bet, not the odds of the hands. Every chip you bet loses the same expected percentage, whatever came before.
What systems do change is the shape of your results. Martingale produces many small wins and occasional huge losses, and table limits stop the doubling long before it "guarantees" a win. We tested Martingale, D'Alembert and Fibonacci against flat betting over 200,000 roulette sessions in our roulette strategy test: none of them beat the house edge, and blackjack works the same way.
Card counting: the one way past the edge
Card counting tracks which cards have already been dealt. When the remaining shoe holds many tens and aces, the player has an edge, and counters bet more. It's legal, but casinos can refuse to deal to you, and it only works when the shoe isn't reshuffled after every hand.
That rules it out for most online blackjack, which reshuffles each hand, and for continuous shuffling machines. Our card counting guide explains the Hi-Lo count and when it can work.
How to win at blackjack: a realistic plan
You can't control the cards, but you can control everything else:
- Learn basic strategy with free play first. Our free blackjack game shows the correct play for every hand and tracks your accuracy.
- Pick the best table you can find: 3:2, S17, double after split.
- Set a session budget and a stop point before you start, and don't chase losses with bigger bets.
- Skip insurance and side bets.
- Accept the swings. A good session isn't proof that a system works, and a bad one isn't proof that it's rigged.
Common blackjack strategy mistakes
- Standing on soft 17 (ace + 6). It can't bust with one card, and 17 rarely wins.
- Not doubling 11 against a dealer 10. The chart doubles it.
- Splitting 10s. You're breaking up a 20.
- Standing on 12 against a 2 or 3. The dealer busts less from those cards than from 4 to 6.
- "Never bust" play: always standing on 12 to 16 against high cards gives up a lot.
- Taking even money on a blackjack against an ace. It's insurance under another name.
Learn more
- Our blackjack rules guide covers the basics, from card values to splitting
- When to split in blackjack, pair by pair
- Blackjack trainer for drilling single hands
Back to the blackjack guides hub.
Frequently asked questions
What is the best strategy for blackjack?
Basic strategy. It's a chart that gives the best play for each of your hands against each dealer upcard, worked out by computer for a given set of rules. In our simulation of a 6-deck S17 game, following it left a house edge of about 0.47%. No other in-game decision method does better without tracking cards.
How do you win at blackjack?
In any single session, you win by being lucky on top of playing well. Over the long run, the house keeps a small edge however you play, unless you count cards in a game where that works. What you control is how small that edge is: use basic strategy, play 3:2 tables, prefer S17 and double after split, and avoid side bets and insurance.
What's the easiest blackjack strategy to remember?
Start with six rules: stand on hard 17 or more, hit hard 8 or less, double 11 against anything but an ace, always split aces and 8s, never split 10s or 5s, and with 12 to 16 stand against a dealer 2 to 6 but hit against 7 to ace (except hit 12 against a 2 or 3). Then learn the soft hands.
Do betting systems like Martingale work in blackjack?
No. Changing bet sizes doesn't change the house edge on each hand, so the expected loss is the same percentage of everything you bet. Martingale turns many small wins into rare large losses and runs into table limits. Our roulette test of Martingale, D'Alembert and Fibonacci over 200,000 sessions shows the same pattern.
Should I take insurance in blackjack?
Not with basic strategy. Insurance pays 2:1 when the dealer has blackjack, but in a 6-deck game the hole card is a ten only about 30.8% of the time when you hold no tens yourself (96 of 311 cards). The bet needs a 33.3% chance to break even, so it loses about 7.4% of what you put on it.
Is it better to hit or stand on 16 against a 10?
Hit, unless your table offers surrender, in which case basic strategy surrenders. Both hitting and standing lose more often than they win, but standing loses slightly more because the dealer with a 10 showing makes 17 or better about 77% of the time after checking for blackjack.
Sources
- 4-Deck to 8-Deck Blackjack Strategy — Wizard of Odds. Basic strategy charts for 4-8 decks, H17 and S17
- Blackjack Rule Variations — Wizard of Odds. 6:5 -1.39%; H17 -0.22%; no DAS -0.14%; single deck +0.48%; double deck +0.19%; 4 decks +0.06%; 6 decks +0.02% (vs 8-deck S17 baseline); late surrender +0.07%
- Blackjack Basics — Wizard of Odds. Card values; split; double; push; blackjack pays 3 to 2
- Blackjack: How to Play — Bicycle Cards. Face cards 10, Ace 1 or 11; split; double down; push returns the bet