Blackjack rules VII
The value of the ace card in a blackjack game needs to be assigned carefully as it has two possible point values and is assigned according to the rank of other cards in the player’s hand. A blackjack hand can either be a soft total or a hard total depending on whether the value of the ace card taken as 1 or 11 makes the total hand value exceed 21 or not. So, for a hand holding an ace and a 4 card, the best possible value for the hand would be 15, which is lower than 21 and hence the hand becomes a soft 15. The significance of a soft total is that this enables the player to draw another card without risking to get busted which happens when his hand value exceeds 21. Now on drawing another card, say an 8 card, the players hand becomes 23 if ace is taken as 11 and the hand gets busted. So, now the hand is called a hard 15 and it indicates that the ace card now must be valued at 1 so as to avoid the total from exceeding 21. Interestingly if instead of an 8 card, the player had drawn, say, a 5 card, his hand total would still be soft 15 as the hand value, taking the ace card as 11, would stand at 20 which is lesser than the limit value of 21.
Since in the game of blackjack, the total 21 when reached by the player or the dealer after receiving only the first two cards, the value of ace is invariably calculates as 11. In this case, since the total is a blackjack or 21, the term ‘soft’ is not used. However the value of the second ace card which may be dealt as either the second and/or the third card is always 1 because otherwise the hand will get busted.

