What does it mean when basic strategy says 'D' or 'double'?

'D' means double down — place an additional bet equal to your original wager and receive exactly one more card. If your casino does not allow doubling on that hand (some games restrict doubling to 9-11 or 10-11), the fallback action is hit. The strategy chart cells often show this as 'Ds' for soft hands, meaning double if allowed, otherwise stand.

Should I always split aces and 8s in blackjack?

Yes — these are the two universal split rules. Splitting aces gives you two strong starting hands, even though most casinos restrict you to one card on each split ace. Splitting 8s turns a poor 16 (the worst hand in blackjack) into two hands of 8 each, which both have a chance to make 18 — a meaningful improvement, even when the dealer shows a 9, 10, or ace.

Are all the tools on this page actually free?

Yes. Every tool listed here is free to use forever — no signup, no trial, no hidden subscription. The GTO Postflop Solver runs entirely in your browser. The pot odds calculator is a single page. We don't gate poker tools behind paywalls or accounts.

Do I need to install anything to use these tools?

No. Everything runs in your web browser. Chrome, Firefox, Safari, Edge — all modern browsers work. Mobile works for most tools, with desktop being smoother for the bigger ones like the GTO solver.

What is a GTO solver and do I need one?

A GTO (Game Theory Optimal) solver computes the mathematically best decisions in poker spots — when to bet, how often to bluff, what hands to call with. Serious players study with one. Casual players don't need one to enjoy poker, but anyone curious about the math underneath the game can poke around for free here.

How are these tools different from PokerTracker, GTO Wizard, or PioSOLVER?

They're free and open. The GTO solver here is wasm-postflop, an open-source engine that produces results essentially identical to PioSOLVER ($1,500). The pot odds calculator does what every paid 'poker odds app' does. We're not building paid alternatives — we're putting the math in everyone's reach.

When will the other 'Coming Soon' tools launch?

Rolling out one at a time, no hype, no pre-orders. The order is roughly: equity calculator, ICM calculator, preflop hand chart, basic strategy chart for blackjack, then guides. Check back, or follow us for launch announcements. We'd rather ship one good tool than ten half-finished ones.

Can I suggest a tool you should build?

Yes, please. Drop a note through the Contact page or post on the forum. The 'Coming Soon' list isn't fixed. If 50 people ask for the same thing, it jumps the queue.

♠ Free Blackjack Tool

Blackjack Basic Strategy Chart

The mathematically optimal play for every blackjack hand — switchable between S17 and H17 rule sets. Cross-checked against Wizard of Odds, Blackjack Apprenticeship, and BlackjackInfo. Always free.

Built for 4–8 deck shoe games with double after split allowed and late surrender available. The strategy is bulletproof for these rules — adjust slightly if your game differs (notes below the chart).

HHit SStand DDouble (else hit) DsDouble (else stand) PSplit RSurrender (else hit)

Hard totals

Hand has no ace, or the ace can only count as 1. Find your total on the left, dealer's up card on top.

Hard totals strategy — 4 to 8 decks
	2	3	4	5	6	7	8	9	10	A

Soft totals

Hand contains an ace counted as 11. The ace gives you flexibility — you can't bust on the next card.

Soft totals strategy — 4 to 8 decks
	2	3	4	5	6	7	8	9	10	A

Pair splitting

When you're dealt two cards of the same rank. Assumes double after split (DAS) is allowed at your table.

Pair splitting strategy — 4 to 8 decks, DAS allowed
	2	3	4	5	6	7	8	9	10	A

Late surrender — when allowed

If your casino offers late surrender (forfeit half your bet, walk away from the hand after the dealer checks for blackjack), use it in these specific spots:

If surrender isn't offered, fall back to the action shown in the hard totals chart.

H17 changes you're seeing

When the dealer hits soft 17, these specific cells differ from the standard S17 chart:

Hard 11 vs. Ace — Double instead of hit
Hard 15 vs. Ace — Surrender (else hit) — was hit in S17
Hard 17 vs. Ace — Surrender (else stand) — was stand in S17
Pair of 8s vs. Ace — Surrender (else split) — was split in S17
Soft 18 vs. 2 — Double if allowed, else stand — was stand in S17
Soft 19 vs. 6 — Double if allowed, else stand — was stand in S17

How basic strategy works

Basic strategy is the mathematically optimal play for every blackjack hand, derived from billions of computer-simulated rounds. It cuts the casino's edge from roughly 2% — what you get from playing on instinct — down to about 0.5%. That's the smallest house edge of any common casino game, and it's the floor every counter, advantage player, and recreational winner builds from.

The chart above is built for the most common live casino game: a 4-to-8 deck shoe, with doubling allowed on any two cards, doubling after splits allowed, and late surrender. If those rules match your casino, the chart is exact. If they don't, the strategy is still very close — the changes are listed below.

Reading the chart

Find your hand on the left axis. Find the dealer's up card on the top. Where they meet is your action. H is hit, S is stand, D is double down (or hit if doubling isn't allowed on that hand), Ds is double if allowed otherwise stand, P is split, and R is surrender if available, otherwise hit.

Why basic strategy looks counterintuitive

The chart makes you do things that feel wrong. Hitting a 16 against a dealer's 7. Splitting 8s against a 10 even though it doubles your loss when you lose. Standing on 12 against a 4. These plays exist because the dealer's up card tells you everything about how their hand will likely finish — and the math always wins over instinct, no matter how strongly your gut disagrees.

The rules that change the strategy

If your game has different rules, the strategy shifts:

Single deck or double deck — A handful of cells shift because the effect of card removal is more pronounced. Use the 4–8 deck chart as a foundation and study the few specific deviations from Wizard of Odds for those games.
No surrender — Treat all R cells as H (hit) for hard 15 and pair of 8s, or S (stand) for hard 17.
No double after split — Don't split 4s. Don't split 6s vs. 2. Don't split 2s or 3s vs. 2 or 3.
Doubling restricted to 9–11 only — Treat all Ds and soft-double cells as the fallback action (stand or hit).
6:5 blackjack — Don't play it. The reduced payout for natural 21s wipes out everything basic strategy recovers. It's a worse-than-roulette game pretending to be blackjack.

Where this strategy comes from

The actions in these tables are not opinions. They're the output of running every possible hand combination through computer simulation millions of times each, picking the action with the best long-run expected value, and putting it in the corresponding cell. The work was originally done in the 1950s and 60s by Roger Baldwin, Edward Thorp, and others, then refined over decades by analysts running larger simulations. Modern verification matches across Wizard of Odds, Blackjack Apprenticeship, and BlackjackInfo's strategy engine, all of which produce the same chart for these rules.

What's next

Once you have basic strategy memorized cold, the next step is card counting — tracking the deck's ratio of high to low cards to know when the deck favors you. The complete card counting toolkit is now live: the 9 counting systems comparison, the true count calculator, and the Illustrious 18 + Fab 4 deviation chart. The long-form basic strategy article covers the strategy in plain English with worked examples, and the card counting 101 guide introduces the Hi-Lo system.

Frequently asked questions

The questions blackjack players ask most often.

What is blackjack basic strategy?

Basic strategy is the mathematically optimal way to play every blackjack hand based on your cards and the dealer's up card. Derived from billions of computer simulations, it cuts the casino's edge from around 2% down to roughly 0.5% — the smallest house edge of any common casino game.

What is the difference between S17 and H17 basic strategy?

S17 means the dealer stands on a soft 17. H17 means the dealer hits a soft 17. Counterintuitively, S17 is better for the player. The strategies differ in a handful of cells: in H17 you double 11 vs. ace, surrender 15 vs. ace, surrender pair of 8s vs. ace, surrender 17 vs. ace, and double soft 18 vs. 2 and soft 19 vs. 6.

Does basic strategy work in single-deck or double-deck blackjack?

The 4–8 deck strategy here is excellent for any multi-deck shoe game. Single and double-deck have a few subtle deviations because card removal effects are more pronounced. Use this as a foundation and study the small list of single/double-deck specific deviations from Wizard of Odds if those games are your regular play.

What does it mean when the chart says "D" or "double"?

"D" means double down — place an additional bet equal to your original wager and receive exactly one more card. If your casino doesn't allow doubling on that hand, the fallback is hit. "Ds" means double if allowed, otherwise stand — used for soft hands where standing is the correct fallback.

Should I always split aces and 8s?

Yes — the two universal split rules. Splitting aces gives you two strong starting hands. Splitting 8s turns a poor 16 into two hands of 8 each, which both have a chance to make 18 — a real improvement, even when the dealer shows 9, 10, or ace.

Should I take insurance in blackjack?

No. Insurance is a side bet that pays 2 to 1 if the dealer has blackjack. Mathematically, the dealer has roughly a 30% chance of having a 10 in the hole — making insurance a losing bet by about 7% of the bet size. The only exception is for card counters tracking deck composition. Basic strategy players: always decline.

How accurate is the basic strategy on this page?

The strategy here was cross-checked against Wizard of Odds, Blackjack Apprenticeship, and BlackjackInfo. All three sources derive from the same underlying computer simulations and produce identical results for the standard rule sets shown. If you find a discrepancy with another source, check the rules: small differences (single-deck, surrender allowed, double after split) change a small number of cells.

Is using basic strategy at the table allowed in casinos?

Yes. Casinos allow basic strategy and even sell wallet-sized strategy cards in their gift shops. Many tables permit you to consult a strategy card while playing. What casinos prohibit is using devices to count cards — but basic strategy itself, making mathematically optimal decisions based on your hand and the dealer's up card, is fully legal and welcomed.