Blackjack insurance: what are you actually buying?
Insurance is a separate bet that the dealer has blackjack, offered when the dealer shows an ace. You can usually put up to half your original bet on it, and it pays 2 to 1 if the dealer’s other card is a 10, J, Q or K.
Should you take it? Basic strategy says no. Unless you know the shoe is rich in tens, the payout is too small for the risk. At a 3:2 table that also means declining even money on your own blackjack.
Insurance can win. The round can still break even.
Take an ordinary $20 hand and add the full $10 insurance. If the dealer has blackjack, the insurance wins $20 and the main hand loses $20. The two cancel out: you have not made $20 on the round.
An ordinary hand: not split, not doubled, and a win pays 1 to 1. Holding a blackjack yourself? Use the even-money comparison below.
$30 returned − $30 put down. The insurance win cancels the main-hand loss, and the round breaks even.
Every outcome for the $20 + $10 example
| Result | Main hand | Insurance | Combined |
|---|---|---|---|
| Dealer blackjack | −$20 | +$20 | $0 |
| No blackjack; you lose | −$20 | −$10 | −$30 |
| No blackjack; you push | $0 | −$10 | −$10 |
| No blackjack; you win | +$20 | −$10 | +$10 |
“Pays 2 to 1” is profit on the insurance bet. A winning $10 insurance bet returns $30: $20 profit plus the $10 back. If the dealer does not have blackjack, the side bet loses, even when your main hand goes on to win.
“Even money?” Read the blackjack payout first.
You have a blackjack and the dealer shows an ace. At a 3:2 table, even money settles your hand at once for a 1 to 1 profit: $20 on a $20 bet now, instead of $30 if the dealer does not have blackjack, or a push if the dealer does.
From a fresh shoe, decline even money on a 3:2 blackjack. The uncertain payout is worth more on average, and taking even money comes to exactly the same as taking full insurance.
A $20 bet. Three choices.
| Dealer’s result | Decline insurance | Buy $10 insurance | Take even money* |
|---|---|---|---|
| Dealer has blackjack | $0your blackjack pushes | +$20insurance wins | +$20 |
| Dealer has no blackjack | +$30 | +$20 | +$20 |
| Average at these odds | +$20.78 | +$20.00 | +$20.00 |
At 3:2, declining is worth more on average.
Declining averages about $20.78 profit against a guaranteed $20: about $0.78 more per $20 blackjack, every time this exact spot comes up.
Six decks, with only your A + K and the dealer’s ace known: the dealer has blackjack 95 times in 309 (30.74%). Averages are over many identical spots, not a forecast for this hand.
*A real guaranteed 1 to 1 offer, where the game makes one. At 6:5, buying insurance does not lock in even money, and a table that offers insurance does not necessarily offer even money.
Why full insurance and even money are the same at 3:2
If the dealer has blackjack, your blackjack pushes and the $10 insurance wins $20. If not, your blackjack pays $30 and the insurance loses $10. Either way you are up $20, which is exactly what even money pays. At 6:5 the second route is $24 − $10 = $14, so the two stop being the same.
More than one third of the unseen cards must be tens.
A $1 insurance bet wins $2 or loses $1. If it wins exactly one time in three, the $2 cancels the two $1 losses. One third is break-even; anything above it pays.
In six decks, with only the dealer’s ace known, 96 of the 311 unseen cards are tens: 30.87%. That leaves the insurance bet losing about 7.40% of every dollar put on it. Your own two cards move those figures a little, and the checker below counts them.
Dealer shows an ace. Insurance pays 2 to 1. Nothing else is known unless you add it below. Figures are per $10 insurance bet, separate from your main bet.
I know other cards that have been dealt
Count every other card you know is out of play: earlier rounds since this shoe was shuffled, and other cards showing this round. Leave out your two cards and the dealer’s ace; they are already counted.
Use counts from this shoe only, and clear them after a shuffle. Enter cards you actually saw, not a hunch from recent results. Burn cards nobody saw stay in the unseen pile.
10 + 6 vs A · 6 decks · no other cards known
Decline insurance
95 ten-value cards among 309 unseen cards: the dealer has blackjack 30.74% of the time.
The insurance bet loses about 7.77% of its stake on average. Your main hand is settled separately.
A strong hand does not make insurance a better bet.
Holding two tens takes two of the cards that could have completed the dealer’s blackjack. A 20 feels worth protecting, but those cards make the insurance bet worse: from a fresh six-deck shoe the dealer has blackjack 30.42% of the time instead of 30.74% against 10 + 6, and $10 of insurance returns −$0.87 instead of −$0.78. Your cards change the odds by leaving the shoe, not by how much you like them.
A card counter, or anyone who can reliably keep track of the tens, can sometimes find a shoe rich enough in them. That is the only exception, and it is arithmetic, not a feeling that a blackjack is due. In six decks, twenty-two low cards have to leave with no tens among them before a hand holding no tens crosses the line.
How the odds are worked out
Each deck holds 16 ten-value cards and 36 others. Take out your two cards, the dealer’s ace and any other cards you enter. The chance of dealer blackjack is the tens left divided by every unseen card, the hole card included. An insurance bet of I returns I × (3p − 1) on average, where p is that chance. The comparison with one third uses the exact counts, not the rounded percentage.
When the dealer asks, “Insurance?”
At a table where the dealer checks for blackjack, the offer comes after the first two cards and before the dealer looks. Say “no insurance”, or wave it off; online, press the game’s decline option, whatever it is labelled. Declining is not folding. If the dealer has no blackjack, the hand carries on and you hit, stand, double or split as usual.
No hole-card check? In games where the dealer takes a second card only after everyone has played, a dealer blackjack is settled at the end. Whether it also takes the extra money you put down to double or split depends on the game, and insurance capped at half your original bet does not cover those extra bets.
A few details the insurance prompt does not explain.
Does insurance pay if the dealer draws to 21?
No. It wins only when the dealer’s first two cards are an ace and a ten-value card. An ace, a 5 and another 5 make 21, but not blackjack, and the insurance bet has already lost by then.
Can I insure less than half my original bet?
Where the table allows it, yes. Half is the usual most you can put on, and some online games offer only the full half. A smaller insurance bet covers less of a losing main hand, but it loses the same share of itself: the price per dollar insured does not change.
Why is there no insurance when the dealer shows a 10?
Insurance is offered only against an ace. The dealer can still have blackjack under a ten-value card, and at a table with a hole-card check the dealer looks for it before you act, but there is no side bet to place on it.
Is insurance the same as surrender?
No. Insurance adds a separate bet and leaves your hand in play. Surrender, where it is offered, ends your hand for half your original bet, with no extra money put down.
What does taking insurance every time cost?
About 0.28% of your stake per hand in six decks, counting every hand you play: the dealer shows an ace about one hand in thirteen, and each insurance bet loses about 7.40% of itself on average. A six-deck game where the dealer stands on soft 17 costs 0.46% played correctly, so the habit adds more than half as much again.
One card, one third.
The whole bet, and the whole reason to decline it, in three lines.
It is not protection
Insurance is a separate bet on the hole card. When it wins, your main hand has lost, and the round only breaks even. From a fresh shoe the side bet loses about seven cents in every dollar.
Even money is the same bet
At 3:2, a guaranteed $20 on a $20 blackjack is worth $0.78 less than playing it out. Only at 6:5 does even money come out ahead, and that is a reason to find another table.
Only a count can change it
Tens must be more than a third of the unseen cards. In six decks that takes twenty-two low cards leaving with no tens among them. If you have not counted, you do not know, and the answer is no.