# Blackjack Basic Strategy Calculator

> Blackjack basic strategy chart and expected values computed for your table rules. Computes the blackjack basic strategy for the rules at your table — number of decks, dealer hits or stands on soft 17, double after split, late surrender, which totals may double, 3:2 or 6:5 — from the exact dealer probabilities of the shoe, not from a copied chart. Enter a hand and the dealer’s up card to see the expected value of hit, stand, double, split and surrender. Play money and learning only: basic strategy lowers the house edge but never beats it.

Part of usefulweb.app (https://usefulweb.app/). Part of [Playcards](https://playcards.usefulweb.app/) (ownerApp: playcards). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://playcardsblackjackstrategy.usefulweb.app/ (interactive tool at https://playcardsblackjackstrategy.usefulweb.app/tool)
- JSON API: POST https://playcardsblackjackstrategy.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://playcardsblackjackstrategy.usefulweb.app/api/v1/tool)
- OpenAPI: https://playcardsblackjackstrategy.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://playcardsblackjackstrategy.usefulweb.app/mcp - tool `playcards_blackjack_strategy`

## Inputs
- decks (select): Decks
- h17 (boolean): Dealer hits soft 17
- das (boolean): Double after split allowed
- surrender (boolean): Late surrender allowed
- doubleOn (select): Double on
- bjPays (select): Blackjack pays
- hand (text): Your two cards (optional) - Ranks 2–10, J, Q, K, A separated by a comma.
- dealer (select): Dealer up card (optional)

## Method
- The dealer’s final totals (17–21 or bust) are computed exactly by recursion over the shoe with your two cards and the up card removed, conditioned on the dealer not having blackjack (US peek rule: with an Ace or ten-value up card the dealer checks first, so you only lose your original bet to a blackjack).
- Hit, stand and double are valued with your extra cards drawn from the shoe with removal; a split hand is valued as a hand starting from one card (doubling only with double after split, split Aces get one card each, no re-splitting). Each hard total is averaged over its two-card combinations weighted by probability (total-dependent strategy).
- The house edge sums every starting hand and up card with its probability, pays 3:2 or 6:5 for a natural, and assumes this strategy with no insurance. It is an estimate: re-splitting and composition-dependent plays are not modelled, so published figures can differ by about 0.05 %.

## Limits
- For learning and play money. No strategy removes the casino’s edge; gambling with real money can be addictive.