Measuring Tip: You Are a Ruler!

Measuring Tip: You Are a Ruler!

They don’t call feet, feet, for nothin.’ Measurement started with counting segments of the human body (forearm, hand, finger, foot). So, if you find yourself without a ruler, make sure you know how to count it old-school.

It’s good to know things like the width of the open and closed spans of your hand, the length of a finger and its joints, the actual length of your foot. Memorize them. Write them on your body for a day to remember them.

When I posted the question of anything to add to this ancient of tips on a private maker group on Facebook, several members chimed in:

Matt Friedrichs Similar to knowing body part length: When you don’t have a tape measure with you, find a body part that matches the length, and then measure that part when you get back to the shop. I use this all the time when I’m working on a shed or something and have left the tape around the corner. Or, when I’m trying to match bolts, I compare to fingers.

Ben Daigneau Some fields (geology here) calibrate the length of their stride so they can walk off distances. Not as precise as a foot or a finger. Also, not exactly a body part, but a lot of people wear belts most of the time. I guess a person could have a few known marks on there.

Measuring Sky Angles


You can also use your hands to measure degrees of the sky. There is a method common in astronomy for measuring sky angles. Here’s how they describe it on One Minute Astronomer:

…Your hands and fingers are a remarkably accurate (and convenient) measuring tool. When you hold your hand at arm’s length, you can estimate angles like this:

  • Stretch your thumb and little finger as far from each other as you can. The span from tip to tip is about 25 degrees
  • Do the same with your index finger and little finger. The span is 15 degrees
  • Clench your fist at arms length, and hold it with the back of your hand facing you. The width is 10 degrees
  • Hold your three middle fingers together; they span about 5 degrees
  • The width of your little finger at arm’s length is 1 degree.

Measuring Distance with Your Thumb


I leave you with one more body part measuring trick, using your thumb to measure distance. This is taken from the old Your Body Ruler – A User’s Manual, a doc that has been online since the web Jurassic:

I hold out my arm, look at my thumb, and see a distant car half as high. Cars are about 5 feet (1.5 meters) high. So my thumb appears 10 feet (3 meters) wide. And since I know (see below) my thumb is x30 times as far as it seems tall… I know the car is something like 300 feet (90 meters) away!

Do you have any body ruler tips to share? Please post them in the comments below.

[Header image from Measuring the Sky]

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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. His free weekly-ish maker tips newsletter can be found at

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