A blackjack insurance calculator answers one question: is the dealer’s hidden card a ten often enough to make the side bet pay? Insurance costs half your bet and pays 2 to 1, so it breaks even when more than one in three of the unseen cards is a ten. In a fresh six-deck shoe, with the dealer’s ace and your two small cards showing, tens are 96 of the 309 cards left: 31.1%. The free calculator above says that costs you 6.8% of whatever you insure.
Blackjack insurance calculator: when it’s worth it
Chance of a ten = tens left ÷ cards left Insurance EV per unit = 3 × chance − 1
Late in a shoe it can flip. Say two decks of six have been dealt and only 22 of them were tens. That leaves 74 tens in 208 cards, 35.6%. Now insurance gains about 6.7% of the amount insured, £0.67 on a £10 insurance bet. This is why card counters insure at a Hi-Lo true count of +3 or more: a high count means the shoe is rich in tens.
| Situation | Chance of a ten | Insurance |
|---|---|---|
| Fresh 6-deck shoe | 31.1% | Costs 6.8% |
| Single deck, you hold two tens | 28.6% | Costs 14.3% |
| Single deck, you hold two small cards | 32.7% | Costs 2.0% |
| 6-deck shoe, 2 decks dealt, 22 tens gone | 35.6% | Gains 6.7% |
Even money is the same bet
With a blackjack against an ace, the dealer offers even money: take 1 to 1 now instead of risking a push. That’s exactly the same as insuring your blackjack, and it carries the same edge. Holding a blackjack makes it slightly worse, because your ten is one fewer for the dealer.
Not counting? Then decline insurance every time. For the count itself, the card counting calculator turns a running count into a true count, and the Illustrious 18 lists insurance as the most valuable index play of all.
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