Definition
Insurance is a side bet offered when the dealer's upcard is an Ace. It costs up to half your main bet and pays 2:1 if the dealer's hole card is a 10-value. Otherwise, it loses.
How it works
When the dealer shows an Ace, every player is offered insurance before the dealer checks the hole card. You can wager up to half your main bet. If the dealer reveals a blackjack (10, J, Q, or K underneath), insurance pays 2:1. If the dealer doesn't have blackjack, insurance loses and the hand continues normally.
Insurance is sometimes pitched as "protecting" your hand, but the math says otherwise. It's an independent side bet on whether the dealer's hole card is a 10-value.
Why the math is bad
In a 6-deck shoe, only 16 of every 52 cards are 10-values (10, J, Q, K). That's 30.77% of the deck. For insurance to break even, you'd need 33.3% (one in three) of cards to be 10-values, since the bet pays 2:1.
Because insurance pays 2:1, that ~2.5-point gap triples into roughly a 7.4% house edge on a 6-deck game (the edge varies by deck count, roughly 5.9% at 1 deck up to 7.5% at 8 decks). For every $100 you put on insurance at a 6-deck table, the casino expects to keep about $7.40.
When insurance IS positive EV
Insurance only makes sense for card counters with a high true count. When the deck is rich in 10-value cards (true count of +3 or higher in Hi-Lo), the probability of a dealer 10-value hole card rises above 33.3%, flipping insurance to positive expected value.
Without an active card count, the deck composition is unknown to you. The default assumption is a normal mix, which makes insurance roughly a 7.4% loser on a 6-deck table (the edge varies by deck count).
The simple rule
If you don't have a count, decline insurance. Every time. Even when you have a blackjack against a dealer Ace and the dealer pitches "even money." The pitch sounds like protection; the math is a tax.
Practice in Blackjack Navigator
Blackjack Navigator's coaching system flags insurance as the wrong play unless you've enabled card counting deviations (a v1.1 feature). The Stats tab tracks how often you correctly decline insurance — one of the cleanest behavioral metrics in the app.
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