Age Cards or Calculator Cards is an mentalism effect using specially printed cards. A spectator thinks of a number (his age if the performer would not know it) and is shown several cards with different sets numbers written on each. After identifying only which cards has their number, the performer (without having to even look at the cards) quickly divines their number or age.
The jargon "Age Cards" was in use by 1931 having appeared in magic catalogs.
In the Magic Cauldron No. 45 (October 1972), Edgar Heyl stated that the method made its first appearance in London in Nicholas Hunt's "Newe Recreations" (1631). The trick was advertised in the London daily adviser in 1747 and also was contained in Charles Hutton's Recreations With Mathematics (1801)
By the 1970s, the trick was popular as the "What's your age" trick.