If the uncovered card of the dealer is an ace, player has a right to ask for insurance, before the dealer uncovers his second card. If the player decides to take the insurance then he is allowed to raise his stake by the half of its previous value. This quote, whose value is equal the insurance value and is being kept in a different place on the table. The player that takes insurance assumes that croupier keeps a second card, whose value is 10 (ten, jack, lady and king). In case of loosing, the player is paid out the doubled value of the insurance.

Example:
A player bets 10 $. Dealer handles the cards to players. The player has a value of 19 in his cards. However, croupier’s first card is an ace. The player decides to take the insurance. He has to pay for it 5 $. Croupier checks his second card and it turns out that its value is 10. The player looses his previous stake – 10 $, but he gets the doubled value of the insurance, which is 10 $. Summing up, the player looses 15 $ (10 $ from the previous stake and 5 $ for paying the insurance) and he only gains10 $ (the insurance value 5 $ multiplied by 2). So overall, he looses 5 $.

It is also possible that the player wins and then he loses the money invested in insurance. Applying this reasoning to the situation above it must be that the value of the croupier’s second card is less than 10, for example 7. In this case the player looses the insurance stake 5 $, but he wins the 10 $ bet. Overall he wins.

Moreover, it is possible that the player losses both: his previous stake and the insurance value.

Insurance is usually a disadvantageous deal for players, who can hardly estimate the value of the second card, which is held by croupier. The insurance is always paid out in a relation 2:1 to the invested stake and the positive probability of the croupier’s blackjack is much higher than its negative probability 9:4 (2.25:1). However, both depend on the number of decks played. Even if a player got 21 in a previous stake, it is not recommended to take the insurance. In this situation croupier asks the player about his decision again. In this case, namely the player accepts the payout 2:2 instead of advantageous 3:2. This is the same like taking insurance, loosing its value and being paid the value of the previous stake in relation 3:2. If the player does not agree to this deal, he gets his stake back.