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This was originally written for and posted on Thirteen.org.

I learned to count binary on my fingers while sipping an egg cream in a New York institution, Yonah Schimmel’s Knish Bakery. A friend of mine was explaining simple hardware setups and said he had a cool trick he used at nerd parties. I practiced over and over on the subway ride back to Brooklyn, until counting became a fluid motion. Now, I can easily count up to 1,023 on my hands (though, I’ve yet to find a concrete reason I’d need to do so).

What are Binary Numbers?

The binary numeral system, otherwise known as the base-2 numeral system, represents numeric values using just two symbols: 0 and 1. It is used by almost all modern computers and in circuitry design. Just because it is the foundation of computing does not mean it wasn’t being used before the 20th century. Binary existed even in the ancient world, having been encountered as far back as the 9th century B.C. in China.

Once you understand how it works, doing math with binary numbers is fairly straight forward. Here are some examples:

101 (5)
x 11 (3)
= 1111 (15)

11101 (30)
– 100 (4)
= 11010 (26)

111011110 (478)
+ 100000110 (262)
= 1011100100 (740)

The Secret to Binary Fingers

Most people are aware of how to count up to ten on their ten fingers (or twenty if you use your toes). In China, they have a system for counting up to ten on one hand! With binary, you can count up to 1,023 using both hands.

Each numerical digit has two possible states, 0 or 1. Each anatomical digit, aka your finger, can therefore be such with a raised finger representing “1” and a lowered finger representing “0.” Each successive finger represents a higher power of two, with the rightmost digit representing 2 to the power of zero.

Join me in counting from one to ten on your fingers.

come across some binary in the wild, use this Binary to Decimal Converter to bring it back to a handy dandy integer.

With some practice, you too can make your friends jealous with super cool mental math skills.