Small Business Brief

Productivity, Retail

Barcoding Decoded: How to Read Barcodes for Beginners

Every single store uses barcodes that are read by scanners, but did you know you can actually read these barcodes just by looking at them? That’s right: you don’t need any scanner to be able to interpret them!

Whether you’re just curious about how your skills match up against the machines or you’re trying to implement a barcode system to improve inventory handling, we’ve got you covered. Here’s a guide on how to read barcodes for beginners.

How to Read Barcodes: Understanding the Structure

Here, we’ll list the components that make up a barcode and explain the purpose of each component.

Quiet Zone

This refers to the margins around the barcode symbols. While it may seem trivial, it’s important that the margins are sufficiently wide in order for the barcode to be read by a scanner. Each margin must be at least ten times wider than the narrowest bar width.

Start/Stop Characters

Inside the barcode itself, these characters surround the data and let the scanner know where to start and stop reading. Different types of barcodes use different characters. Some systems use letters, others use asterisks, and sometimes they just use a specific bar pattern.


This is represented by a pattern of black bars and white spaces which can be either narrow or wide. They can have up to four different widths (the smallest is four times smaller than the largest).

Check Digit

This number is present at the end of the data, before the stop character. It calculates a value from the data and makes sure it’s equal to this digit to ensure there is not a “read error”. It essentially doublechecks for any printing errors that may have occurred when the barcode was created. 

How to Read Barcodes: Interpreting the Lines

There are several types of barcodes, but we’re going to stick with how to read barcodes that are 12 digit UPC, which is the most common. While most UPC barcodes have numbers underneath it, some do not. We’ll teach you how to “read” the bars to calculate the 12 digit number that the barcode represents. 

First, find the sets of long lines that extend down past all of the others — there should be three sets made up of two lines each. These lines are not interpreted as numbers by the scanner, but they do break up the data into two chunks that are read differently — we’ll refer to these as left and right.

Next, make sure you can tell apart the different bar and space widths. For now, we’ll refer to these as numbers 1, 2, 3, 4 going from smallest to largest in size.

For the left chunk, start with the first space you see and write down its size. Do this for all spaces and bars until you reach the center (and again, do not decode these center lines). Break these up into sets of four — white-black-white-black.

On the right chunk, you’ll do the same thing but instead, start with the first black bar you see. So now, you’ll again break up the values into sets of four but they will be black-white-black-white.

You should have two sets of six numbers. Each of these four-digit numbers can be translated into one digit. Use the following to convert them:

  • 0 = 3211
  • 1 = 2221
  • 2 = 2122
  • 3 = 1411
  • 4 = 1132
  • 5 = 1231
  • 6 = 1114
  • 7 = 1312
  • 8 = 1213
  • 9 = 3112

And now you finally have your 12 digit UPC number! Be sure to check your work to see if you got the correct number. This c# barcode scanner should do the trick.

How to Read Barcodes: Calculating the Check Digit

As we stated earlier, the number following your data is the check digit. How does the check digit ensure an accurate scan?

Once you have your 12 digits, number their locations from 12 on the left to 1 on the right in descending order. For every odd location (11, 9, 7, etc.), multiply the number by three. Do not change the even location numbers.

Then, add all 12 of these numbers together. Then, take just the last digit of this value and subtract it from ten to get your check value. Let’s demonstrate an example to make it simpler:

Numbers: 8 3 4 7 5 2 1 9 0 6 1 3

Would lead to: 8 3×3 4 7×3 5 2×3 1 9×3 0 6×3 1 3×3

Which gives us: 8 + 9 + 4 + 21 + 5 + 6 + 1 + 27 + 0 + 18 + 1 + 9

This equals 109. Then, 10 – 9 = 1. So our check digit should equal 1 if our scan was correct.

How to Read Barcodes: What the Numbers Mean

Now that you know how to read the bars, let’s talk a little bit about what the numbers mean. 

Typically, the first 6-10 digits, called the company prefix, represent the company selling the product or the company that manufactures the product. So if you’re going to a clothing store, most of the barcodes will probably start the same, but if you’re at the grocery store, they’re likely all very different. 

The numbers following the company prefix are called the item reference, and it’s a specific number to represent the product. The 12th digit is that check digit we discussed above.

However, sometimes the first number in the barcode has a specific meaning. If that first number is a 3, it’s a drug or pharmaceutical product. The next 10 numbers are the U.S. National Drug Code number, and the last digit is the check digit.

If the first digit is a 2, the item is sold by weight. The first 6 digits represent that product’s manufacturer, and the following 5 are used to either identify the product’s weight or to represent the price of a certain weight.

If you want to find out more about a particular bar code, you can always look it up on Barcode Lookup. Type in the barcode number and it should be able to tell you the company name and product.

Now You’re a Barcode-Reading Pro!

We hope that this guide on how to read barcodes has helped make you a barcode-reading master! Are you learning more about barcodes so you can purchase them for your new online business? Check out our 7 simple steps to starting your own online retail business for some great, helpful tips!