Blackjack Insurance and Even Money

A wager paid at 2:1 breaks even when it wins exactly one time in three: the single win returns two units and covers the two losses beside it. Insurance therefore needs one unseen card in three to be worth ten. Four of the thirteen ranks are worth ten, the tens and the three picture cards, a little short of a third, and the shortfall is where the house earns its margin.

With the dealer's ace out of a freshly shuffled six-deck shoe, the hole card is a ten 30.87% of the time. That is the chance the insurance wager wins, and it leaves the house an edge of 7.40% on every unit placed on it, a price many times that of the main hand.

The rule: Insurance pays its way only when more than one unseen card in three is worth ten, and a freshly shuffled deck or shoe never holds that many.

A live shoe can drift above that line as small cards leave it, and a player tracking the cards can spot the moment; the card counting guide gives the count at which the wager turns in the player's favor. An online table reshuffles for every round, so the starting prices on this page are the ones that apply there.

These figures count only the dealer's ace as a known card. The edge is a share of the insurance wager itself, not of the main bet. Taking one ace out of a single deck lifts the share of tens among the cards left more than taking it out of a large shoe, which is why insurance costs least at one deck.

Here the player's two cards are counted as well as the dealer's ace. On a one-seat online table they are the only other cards in view, and they matter because every ten in the player's hand is a ten that cannot be under the ace.

A player who holds 20 made of two ten-value cards has removed two of the very cards the insurance wager needs. From one deck that lifts the house edge on the wager from 5.88% with only the ace known to 14.29%, and from six decks from 7.40% to 8.74%. The hand most often insured is therefore the one that makes the wager worst.

Two small cards work the other way. They leave the remaining cards slightly richer in tens, and from one deck the edge falls to 2.04%. Even that is still a losing wager, and from six decks, at 6.80%, the gain is small. The effect shrinks as decks are added, because two cards out of a large shoe barely change what is left.

Whether the main hand is likely to win plays no part: the wager is settled on the dealer's second card alone, and the player's hand matters only for the cards it has taken out of play.

With a natural in hand against a dealer's ace, the table offers even money: 1:1 on the natural, paid at once. That payment is exactly what insuring the blackjack for half its stake would produce. If the dealer has a ten underneath, the blackjacks push and the insurance half-unit wins two halves, one unit in all; if not, the natural pays one and a half units and the insurance half-unit is lost, which again leaves one unit. Both routes land on the same figure, so the casino simply settles it in advance.

Declining keeps the 3:2 payout alive at the risk of a push. With the player's own ten out of a six-deck shoe, the dealer turns up a blackjack 30.74% of the time, and the rest of the time the natural is paid in full. Over both outcomes, declining averages +103.9 per 100 units bet, while taking even money locks in +100.0.

The key number: Each time even money is accepted from six decks, the certainty costs 3.9 units per 100 units bet, the price of an insurance wager placed on a hand that was already winning.

What the guarantee buys is the removal of the push. Some players value that, but over many naturals declining comes out ahead.

Taking even money returns +100.0 per 100 units bet at every deck count. The dealer's chance of a blackjack here sits a little below the figure in the first insurance table, because the player's natural has already taken one ten out of the cards.

The dealer turns up an ace about once in every 13 rounds. Taking full insurance, half the main stake, at each of those moments raises the house edge of the whole game by 0.28 points from six decks, a point being one unit given up per 100 units of initial bets. Played with basic strategy, the standard game costs 0.41% without the habit, so insuring every ace adds more than half as much again.

The habit costs 0.23 points from one deck, 0.26 from two and 0.29 from eight. These sums are far smaller than the wager's own edge because the wager is half the stake and comes up in only a small share of rounds, yet they land on a game whose whole margin is already measured in fractions of a point.

The basic strategy charts leave insurance out for that reason: no hand on them is improved by it. Insuring every ace sits beside never doubling and never splitting among the costly habits priced on the blackjack tips page.

On a Spanish deck, stripped of the cards marked 10, insurance carries a house edge of 24.74%, against 7.40% on six ordinary decks, as the Spanish 21 page explains. Double Exposure offers no insurance at all, since the dealer's two cards are visible from the start, and the rules that replace it are on the Double Exposure blackjack page.

The other optional wagers placed beside the main hand, from pairs to poker hands, are compared in the blackjack side bets guide. Like them, insurance is a price paid only by choice; play only with money you can afford to lose.