How to Read Bar Codes

Updated February 21, 2017

While it is much easier and faster to have a bar code reading machine read bar codes for you, it is actually possible to read bar codes without one. It makes a fun party trick to have a friend find a bar code, cut the numbers off the bottom and then let you impress the crowd by accurately reading the lines of the bar code.

The bar code is made up of both black lines and white ones.

There are four types of lines. The thinnest line has a value of 1. As they get thicker, the values go up, with the thickest being a value of 4.

The first three bars and the last three bars each form 101, or thin black, thin white, and thin black, to mark the beginning and end of the code. Do not read these lines as part of the code.

A sequence of 01010 marks the middle of the code and looks like five thin lines alternating white and black that jut down further than the rest of the lines in the code. Do not read these lines as part of the code.

Each sequence of four lines represents one digit. Here are the sequences and their corresponding digits. 0 = 3211 1 = 2221 2 = 2122 3 = 1411 4 = 1132 5 = 1231 6 = 1114 7 = 1312 8 = 1213 9 = 3112

Once you have learnt to recognise the line thicknesses and memorised the number sequences that create each digit, just read the code four lines at a time, excluding the 101 at the beginning, the 01010 in the middle and the 101 at the end.

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