Before we had precise, standardized units of measure such as meters and feet, lengths (and even, ocasionally volumes) were reckoned based on the average dimensions of human body parts. In Body-Based Units of Measurement at Interesting Thing of the Day, I listed a few such historical units of measure, which can still come in handy for rough approximations if you don’t have a ruler or tape measure handy.
- cubit: This is the distance from a man’s elbow to the tip of his middle finger, which would be about 18 inches for the average man today. (Men, of course, did the building at the time the cubit was in regular use; a woman’s “cubit” would typically be shorter.)
- foot: It probably goes without saying that the unit foot was based on the length of a man’s foot.
- span: Stretch out the fingers of your hand so that the tip of your thumb is as far away as possible from the tip of your pinky. That distance is called a “span,” which for most people is almost exactly half a cubit.
- handbreadth: The width of your four fingers where they meet the palm—usually about 4 inches—is a handbreadth or sometimes just a “hand.” The height of horses is usually expressed in hands.
- digit: The width of a finger, which tends to be about 13/16 of an inch.
- thumb: The width of a thumb, which was later used as the basis for the inch.
- fathom: If you stretch out your arms to either side of your body as far as they’ll go, the distance between the tips of your middle fingers will be very close to your height, or about six feet—your own feet, that is—a length also known as a fathom.
- handful: Although we normally use the word handful in the informal sense of “just a little bit,” your hand can serve as a fairly repeatable measure of volume for dry goods such as grains, beans, and seeds.