Blackjack insurance bet explained: the 2-to-1 payout and its edge
Insurance is a side bet, offered when the dealer shows an ace, that the hole card is a ten-value card. It stakes half the original bet and pays 2 to 1. Ten-value cards are less than one third of the unseen cards, so the bet carries a house edge.
What the insurance bet is
When the dealer's face-up card is an ace, many tables offer insurance before the dealer checks the hole card. The player may stake up to half of the original bet on the claim that the hole card is worth ten (a ten or a picture card). If it is, the insurance pays 2 to 1; if not, the insurance stake is lost and the hand continues.
It is a separate wager, settled on one card, and it is independent of the hand in front of the player. The ordinary edge of the main hand is covered in where the blackjack house edge comes from; this guide prices the side bet alone. The rules below are the common form, and a table may word them differently, so read the displayed rules.
The fair payout for a one-card event
Suppose a bet wins with probability p and pays n to 1 on the stake. For one unit staked, the average result is p × n − (1 − p). It is zero, or fair, only when n = (1 − p) / p. The idea is the same as in the guide to expected value.
For a payout of 2 to 1, the fair probability solves 2 = (1 − p) / p, which gives p = 1/3. So insurance is a fair bet only if the hole card is worth ten exactly one time in three. Any lower probability gives the house an edge.
Deriving the probability from card counts
A deck has 52 cards, and 16 of them are worth ten (four tens, four jacks, four queens, four kings). With D decks there are 52D cards and 16D ten-value cards. The only card the player knows about for now is the dealer's ace, which is not ten-value.
The hole card is one of the other 52D − 1 cards, each equally likely, so the chance it is ten-value is 16D / (52D − 1). With one deck that is 16/51 ≈ 31.37%. With eight decks it is 128/415 ≈ 30.84%.
The average result per unit of insurance stake is 2p − (1 − p) = 3p − 1. For one deck: 3 × 16/51 − 1 = 48/51 − 51/51 = −3/51 = −1/17 ≈ −5.88%. The same steps give each row of the table.
| Decks | Ten-value cards among unseen cards | Chance hole card is ten-value | Average result per unit staked (3p − 1) | Edge on insurance stake |
|---|---|---|---|---|
| 1 | 16 of 51 | 31.37% | −3/51 = −1/17 | 5.88% |
| 2 | 32 of 103 | 31.07% | −7/103 | 6.80% |
| 4 | 64 of 207 | 30.92% | −15/207 | 7.25% |
| 6 | 96 of 311 | 30.87% | −23/311 | 7.40% |
| 8 | 128 of 415 | 30.84% | −31/415 | 7.47% |
| Endless supply | 4 of 13 | 30.77% | −1/13 | 7.69% |
Every row sits below the 33.33% needed for a fair 2-to-1 payout. The edge grows with the number of decks, which matches the pattern in how deck count changes the blackjack edge.
What the edge means for a real stake
Original bet KES 200, so the insurance stake is KES 100, from a single deck with only the dealer's ace seen. The hole card is ten-value with probability 16/51, which pays KES 200 profit. Otherwise (35/51) the KES 100 is lost.
(16/51 × 200) − (35/51 × 100) = 3,200/51 − 3,500/51 = −300/51 ≈ −KES 5.88
That is 5.88% of the KES 100 insurance stake, every time insurance is taken, on average. In a single round the result is either +KES 200 or −KES 100, so the average is never what happens.
Why the hand you hold changes the numbers
The table counts only the dealer's ace. In a real round the player's own cards are also on the table, and they change what is left in the pack. This is exact, not a matter of opinion: only the cards seen matter.
Single deck, dealer shows an ace, and the player holds two tens. Three cards are seen, and the remaining 49 contain 14 ten-value cards. Then 3 × 14/49 − 1 = 42/49 − 49/49 = −7/49 = −1/7 ≈ −14.29%.
If the player's two cards are a 5 and a 6, all 16 ten-value cards remain among 49. Then 3 × 16/49 − 1 = 48/49 − 49/49 = −1/49 ≈ −2.04%.
Holding ten-value cards makes the insurance worse, and holding small cards makes it cheaper, though it stays below zero in both cases. The edge reaches zero only when the unseen cards contain a ten-value share of one third or more. That needs knowledge of many cards already dealt from a pack that is not reshuffled, which is the subject of why card counting does not work in online blackjack.
Even money
Even money is insurance offered to a player who holds a natural blackjack (an ace and a ten-value card). The choice has a clear structure, and the sums can be checked.
Original bet KES 100 with a natural paid 3 to 2, single deck. The player holds an ace and a ten, plus the dealer's ace, so 3 cards are seen and 15 of the other 49 are ten-value.
Take insurance (KES 50). If the dealer has a natural, the main bet is a push and insurance wins KES 100: net +KES 100. If not, insurance loses KES 50 and the natural wins KES 150: net +KES 100. The result is +KES 100 in both cases.
Decline. With probability 15/49 the dealer has a natural and the hand is a push (KES 0). With probability 34/49 the natural wins KES 150. The average is 34/49 × 150 = 5,100/49 ≈ KES 104.08.
Taking even money gives up about KES 4.08 on average to remove the variation. It does not create a profit, and the arithmetic is the same cost as the insurance edge, only presented as a certain result. A push, as used here, is explained in what a push means in blackjack.
Why the name misleads
Insurance sounds like a way of covering a loss. In the numbers above, the bet does not lower the average cost of a round, and it adds its own edge on top of the hand. It behaves like any other side bet with a fixed pay table, as set out in why blackjack side bets cost more.
What it does change is the spread of results. After insurance, a round in which the dealer has a natural ends closer to level, and a round in which the dealer does not ends slightly lower. That is a difference in swings, not in the average.
Finding the rules of a table in Kenya
Whether insurance is offered, and on what terms, belongs to the rules of the table. Regulation 20(2) of the Gambling Control (Conduct of Gambling Operations) Regulations, 2026 says a licensee shall display clearly the rules of games, odds, house edge and average return to the player. Regulation 45(1) says a person operating an online gambling activity shall ensure the game rules are clearly displayed before a player places any wager.
The figures here assume a 2-to-1 payout, a half-bet stake and standard 52-card decks, and they use no figure from any operator. Where a table shows a different payout, the same formula applies: compare the chance of a ten-value card with 1 / (n + 1). Gambling is addictive; play responsibly, and see the responsible gambling page for limits and the GRA helpline. This content is for adults aged 18+.
Questions and answers
Does insurance protect my original bet?
Not in the sense the name suggests. It is a separate bet on the hole card. If the dealer has a natural, the insurance win covers the loss on the original bet, and if not, the insurance stake is lost and the hand plays on, so the bet does not lower the average cost of the round.
Why does a 2-to-1 payout still favour the house?
The payout is fair only if a ten-value card is hidden exactly one time in three. With a single deck and only the dealer's ace seen, it is 16 in 51 (31.37%), and with many decks it approaches 4 in 13 (30.77%). Both are below one in three, so the bet loses on average.
What is even money?
Even money is the name for taking insurance when the player holds a natural blackjack. The result is the same in every case, a profit equal to the original bet, so it is a choice between a certain even-money win and the chance of the full natural payout.
Does the number of decks change the insurance edge?
Slightly. Counted from the dealer's ace alone, the edge is about 5.88% of the insurance stake with one deck and about 7.47% with eight. More decks make ten-value cards slightly rarer among the unseen cards, which is the direction of the change.
Where does a Kenyan player find the insurance rules of a table?
In the game rules displayed by the operator. Regulation 45(1) of the 2026 Conduct of Gambling Operations Regulations requires an online operator to display the game rules before a player places any wager, and regulation 20(2) requires rules, odds, house edge and average return to be displayed.