Blackjack Basic Strategy Calculator

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.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }

Blackjack Basic Strategy Calculator

Enter your hand and the dealer's upcard to get the statistically optimal Basic Strategy action based on standard multi-deck (4–8 deck) casino rules.

Hand Type

Hard Total Soft Hand (Ace + card) Pair

Your Hard Total (5–20)

Your Other Card (2–9, Ace=soft 12–20)

A+2 (Soft 13) A+3 (Soft 14) A+4 (Soft 15) A+5 (Soft 16) A+6 (Soft 17) A+7 (Soft 18) A+8 (Soft 19) A+9 (Soft 20)

Your Pair

2s 3s 4s 5s 6s 7s 8s 9s 10s / Face Cards Aces

Dealer Upcard

2 3 4 5 6 7 8 9 10 / Face Card Ace

Get Optimal Action Your optimal action will appear here.

function blaUpdateHandInputs() { var type = document.getElementById('bla-hand-type').value; document.getElementById('bla-hard-row').style.display = (type === 'hard') ? '' : 'none'; document.getElementById('bla-soft-row').style.display = (type === 'soft') ? '' : 'none'; document.getElementById('bla-pair-row').style.display = (type === 'pair') ? '' : 'none'; }

function blaCalc() { var type = document.getElementById('bla-hand-type').value; var dealer = parseInt(document.getElementById('bla-dealer-card').value); var action = ''; var handDesc = ''; var explanation = '';

// ── PAIR STRATEGY (multi-deck, DAS allowed) ────────────────────────────── // Source: Wizard of Odds multi-deck basic strategy var pairStrategy = { // pair card → [dealer 2..10, A] 2: ['SP','SP','SP','SP','SP','SP','H','H','H','H'], 3: ['SP','SP','SP','SP','SP','SP','H','H','H','H'], 4: ['H','H','H','SP','SP','H','H','H','H','H'], 5: ['Dh','Dh','Dh','Dh','Dh','Dh','Dh','Dh','H','H'], 6: ['SP','SP','SP','SP','SP','H','H','H','H','H'], 7: ['SP','SP','SP','SP','SP','SP','H','H','H','H'], 8: ['SP','SP','SP','SP','SP','SP','SP','SP','SP','SP'], 9: ['SP','SP','SP','SP','SP','S','SP','SP','S','S'], 10: ['S','S','S','S','S','S','S','S','S','S'], 11: ['SP','SP','SP','SP','SP','SP','SP','SP','SP','SP'] };

// ── SOFT STRATEGY (multi-deck) ──────────────────────────────────────────── // Indexed by other card (2–9), dealer 2..10,A var softStrategy = { 2: ['H','H','H','Dh','Dh','H','H','H','H','H'], // A+2 = soft 13 3: ['H','H','H','Dh','Dh','H','H','H','H','H'], // A+3 = soft 14 4: ['H','H','Dh','Dh','Dh','H','H','H','H','H'], // A+4 = soft 15 5: ['H','H','Dh','Dh','Dh','H','H','H','H','H'], // A+5 = soft 16 6: ['H','Dh','Dh','Dh','Dh','H','H','H','H','H'], // A+6 = soft 17 7: ['Ds','Ds','Ds','Ds','Ds','S','S','H','H','H'], // A+7 = soft 18 8: ['S','S','S','S','S','S','S','S','S','S'], // A+8 = soft 19 9: ['S','S','S','S','S','S','S','S','S','S'] // A+9 = soft 20 };

// ── HARD STRATEGY (multi-deck) ──────────────────────────────────────────── // Indexed by hard total (5–20), dealer 2..10,A var hardStrategy = { 5: ['H','H','H','H','H','H','H','H','H','H'], 6: ['H','H','H','H','H','H','H','H','H','H'], 7: ['H','H','H','H','H','H','H','H','H','H'], 8: ['H','H','H','H','H','H','H','H','H','H'], 9: ['H','Dh','Dh','Dh','Dh','H','H','H','H','H'], 10: ['Dh','Dh','Dh','Dh','Dh','Dh','Dh','Dh','H','H'], 11: ['Dh','Dh','Dh','Dh','Dh','Dh','Dh','Dh','Dh','H'], 12: ['H','H','S','S','S','H','H','H','H','H'], 13: ['S','S','S','S','S','H','H','H','H','H'], 14: ['S','S','S','S','S','H','H','H','H','H'], 15: ['S','S','S','S','S','H','H','H','Rh','H'], 16: ['S','S','S','S','S','H','H','Rh','Rh','Rh'], 17: ['S','S','S','S','S','S','S','S','S','Rs'], 18: ['S','S','S','S','S','S','S','S','S','S'], 19: ['S','S','S','S','S','S','S','S','S','S'], 20: ['S','S','S','S','S','S','S','S','S','S'] };

// dealer index: 2→0, 3→1, ..., 10→8, A(11)→9 var dealerIdx = (dealer === 11) ? 9 : (dealer - 2);

var codeMap = { 'H': { short: 'HIT', color: '#e74c3c', detail: 'Hit — take another card.' }, 'S': { short: 'STAND', color: '#27ae60', detail: 'Stand — take no more cards.' }, 'Dh': { short: 'DOUBLE DOWN', color: '#2980b9', detail: 'Double Down (if not allowed, Hit).' }, 'Ds': { short: 'DOUBLE DOWN', color: '#2980b9', detail: 'Double Down (if not allowed, Stand).' }, 'SP': { short: 'SPLIT', color: '#8e44ad', detail: 'Split the pair into two hands.' }, 'Rh': { short: 'SURRENDER', color: '#e67e22', detail: 'Surrender (if not allowed, Hit).' }, 'Rs': { short: 'SURRENDER', color: '#e67e22', detail: 'Surrender (if not allowed, Stand).' } };

var code = '';

if (type === 'pair') { var pairCard = parseInt(document.getElementById('bla-pair-card').value); var row = pairStrategy[pairCard]; if (!row) { blaShowError('Invalid pair card.'); return; } code = row[dealerIdx]; var pairName = (pairCard === 11) ? 'Aces' : (pairCard === 10) ? '10s' : pairCard + 's'; handDesc = 'Pair of ' + pairName + ' vs Dealer ' + (dealer === 11 ? 'Ace' : dealer);

} else if (type === 'soft') { var softCard = parseInt(document.getElementById('bla-soft-card').value); var row = softStrategy[softCard]; if (!row) { blaShowError('Invalid soft hand.'); return; } code = row[dealerIdx]; var softTotal = softCard + 11; handDesc = 'Soft ' + softTotal + ' (A+' + softCard + ') vs Dealer ' + (dealer === 11 ? 'Ace' : dealer);

} else { var hardTotal = parseInt(document.getElementById('bla-hard-total').value); if (isNaN(hardTotal) || hardTotal 20) { blaShowError('Hard total must be between 5 and 20.'); return; } // Clamp totals ≤4 to always hit, ≥21 edge cases if (hardTotal 20) hardTotal = 20; var row = hardStrategy[hardTotal]; if (!row) { blaShowError('Invalid hard total.'); return; } code = row[dealerIdx]; handDesc = 'Hard ' + hardTotal + ' vs Dealer ' + (dealer === 11 ? 'Ace' : dealer); }

var info = codeMap[code]; var dealerStr = (dealer === 11) ? 'Ace' : dealer;

document.getElementById('bla-result').innerHTML = '' + '' + handDesc + '' + '' + info.short + '' + '' + info.detail + '' + ''; }

function blaShowError(msg) { document.getElementById('bla-result').innerHTML = '⚠ ' + msg + ''; }

#### Strategy Tables

This calculator implements the multi-deck (4–8 deck) Basic Strategy for standard casino rules: dealer stands on soft 17, double after split (DAS) allowed, late surrender available. Three decision tables are used:

• Hard Totals (5–20): Decisions based solely on your numeric total and dealer upcard. No aces counted as 11.
• Soft Hands (Soft 13–20): One ace counted as 11 plus one other card (2–9). Doubling opportunities arise on soft 13–18 against weak dealer upcards.
• Pairs: Whether to split depends on the pair rank and dealer upcard. Always split Aces and 8s; never split 10s or 5s.

Action codes: H = Hit · S = Stand · Dh = Double (else Hit) · Ds = Double (else Stand) · SP = Split · Rh = Surrender (else Hit) · Rs = Surrender (else Stand)

Basic Strategy reduces the house edge to approximately 0.4%–0.6% in standard multi-deck games.

#### Assumptions & References

• Dealer stands on soft 17 (S17 rules).
• Double After Split (DAS) is permitted.
• Late Surrender is available (if not, follow the fallback action shown).
• Re-splitting aces is not assumed; split aces receive one card each.
• Strategy source: Wizard of Odds multi-deck basic strategy charts (wizardofodds.com).
• Reference: Beat the Dealer by Edward O. Thorp (1962) — foundational work on blackjack strategy.
• Reference: Griffin, P. (1999). The Theory of Blackjack. Huntington Press.
• This calculator provides the statistically optimal action to minimise the house edge over the long run. It does not account for card counting or side bets.

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References

• ANA
• Life Services Authority