Look up the optimal play for any hand against any dealer upcard.
Blackjack is one of the few casino games where the player's decisions significantly affect the outcome. Basic strategy, a mathematically derived set of rules for every possible hand combination, reduces the house edge to about 0.5% (compared to 2-5% for most other table games). This calculator shows the optimal play for any hand against any dealer upcard and calculates the probabilities for each possible outcome.
Enter your hand (two or more cards) and the dealer's visible upcard. The calculator shows the recommended action (hit, stand, double down, split, or surrender) based on basic strategy, the probability of winning with each option, and the expected value of each decision. It uses standard blackjack rules (dealer stands on soft 17, double after split allowed).
Hard hands: Always hit on 8 or less. Stand on 17+. The decisions for 9-16 depend on the dealer's upcard. Soft hands (with an ace): More aggressive because you cannot bust on one hit. Double down more often. Pairs: Always split Aces and 8s. Never split 10s or 5s. Other pairs depend on the dealer's card. The Poker Odds Calculator covers card probability for poker.
Blackjack offers some of the best odds in any casino game. With perfect basic strategy, the house edge drops to approximately 0.5% in a standard 6-deck game with favorable rules. Without basic strategy, the average player faces a house edge of 2% to 5%. The key mathematical insight is that each card removed from the shoe changes the probabilities of all remaining outcomes.
Card counting systems like Hi-Lo assign values to cards (+1 for 2-6, 0 for 7-9, -1 for 10-A) to track the ratio of high to low cards remaining in the shoe. A "true count" divides the running count by the estimated number of remaining decks. When the true count is positive, the remaining shoe favors the player. Casinos counter this by using multiple decks, shuffling more frequently, and monitoring betting patterns.
The probability of being dealt a natural blackjack (Ace + 10-value card) from a fresh 6-deck shoe is approximately 4.75%. The dealer busts approximately 28% of the time. Standing on 12 against a dealer 2 results in a loss 65% of the time, but hitting results in a bust 31% of the time. These precise probabilities are why basic strategy charts exist and the Probability Calculator can help explore similar calculations. Insurance is almost always a bad bet: the expected value is negative unless you are counting cards and the true count is +3 or higher.
Card counting is a legal but casino-discouraged strategy that tracks the ratio of high cards to low cards remaining in the shoe. The Hi-Lo system assigns +1 to cards 2-6 (low), 0 to cards 7-9, and -1 to cards 10-A (high). A positive running count means more low cards have been dealt, leaving more high cards in the deck, which favors the player. The "true count" divides the running count by the estimated number of remaining decks. At a true count of +2 or higher, basic strategy adjustments and increased bet sizes create a mathematical edge for the player. However, casinos use multiple decks (6 to 8), frequent shuffling, and surveillance technology to minimize the effectiveness of counting. Online blackjack uses continuous shuffling, making counting impossible.