Hand Counting by Twelves

Richard Rathe 2023, Ancient Technology

Ever wonder why we sometimes count things by the dozen, or why there are 60 minutes in an hour? We may have the ancient Babylonians (or earlier societies) to thank. They came up with this ingenious way to keep track of large numbers using only their two hands. There are variations on this theme, but it becomes pretty obvious if you have a hand with four fingers, with three bones each, and a thumb.

The procedure is simple:

1. Start with the base of the right little finger
2. Count with the right thumb up that finger to 3
3. Move to the base of the next finger and repeat
4. When you get to the tip of the index finger that's 12
5. Start again, but extend the left little finger for 12
6. Now start counting 13, 14, 15 on the right hand
7. When the left hand is fully open you've counted to 60

If you use the thumb as a counter on the left hand you can get to 120!