Barcodes are all around us. While barcode scanners are the standard tools for reading and decoding barcodes, it is also possible to interpret them manually.
Learning how to read barcodes without a scanner can be helpful for troubleshooting, educational purposes, or when you need to verify product information manually.
This guide explains the basics of barcodes and provides steps for interpreting the information encoded within them.
Barcodes be categorised into two main types: 1D (one-dimensional) and 2D (two-dimensional) barcodes.
1D barcodes, also known as linear barcodes, consist of a series of vertical lines and spaces of varying widths. These barcodes are read horizontally from left to right by a barcode reader. They can encode alphanumeric characters only.
Examples of 1D barcodes include:
2D barcodes use patterns of squares, dots, or other shapes to encode data horizontally and vertically. They can store various data types, such as alphanumeric characters, binary data, and special symbols.
Common examples of 2D barcodes include:
To manually decode a barcode, it’s essential to understand its basic structure. Barcodes encode information through a combination of bars (black lines) and spaces (white gaps) of varying widths and patterns.
1D barcodes consist of several key components:
1D barcodes encode information using a combination of black and white lines representing binary data, where dark lines are treated as 1s and white spaces are treated as 0s.
Each digit in the entire barcode is represented by seven equal-sized vertical blocks. These blocks ensure that each digit occupies the same horizontal space within the barcode.
Here’s how each number from 0 to 9 is represented in a barcode:
Alphabets, special characters, and other data sets are also easily convertible to binary form. They are represented in the same manner as numerical digits in barcodes. Each character is assigned a binary pattern corresponding to a unique sequence of black and white lines.
Interpreting a barcode correctly involves understanding how the encoded data translates into readable information. Follow these steps to manually decode a linear barcode.
Barcodes can be visually identified by looking at their structure and pattern.
Determine if the barcode image is a UPC barcode, EAN barcode, Code 39, or another type of 1D barcode. This will help you understand the encoding patterns specific to that barcode type.
Refer to our article, “Identifying Barcode Types Visually,” to learn the skill of identifying barcodes visually.
Familiarise yourself with the start, middle, and stop patterns. These patterns are unique sequences of bars and spaces that signal the beginning, middle (for some barcodes), and end of the barcode.
The typical structure includes.
Each digit is represented by a specific pattern of black and white lines. Use the reference patterns (as provided in the previous section) to match and decode each set of seven blocks.
Let’s walk through an example of decoding a UPC-A barcode commonly found on retail products.
A UPC-A barcode consists of 12 numeric digits grouped into a 1-5-5-1 format. This means the barcode starts with a single digit, followed by two groups of five digits each, and ends with a single digit.
The barcode is divided into three sections by sets of longer parallel lines at the beginning, middle, and end.
The start pattern for a UPC-A barcode is a sequence of three bars represented as 101. This pattern indicates the beginning of the barcode.
Each vertical bar in the barcode can have one of four different widths. These widths are classified from thinnest to thickest as 1, 2, 3, or 4.
To decode the barcode, you need to identify the width of each bar. Using a magnifying glass can help distinguish between similar widths.
Start by examining the bars on the left side, between the start pattern and the middle pattern. Measure the thickness of each bar, starting with the first white bar.
Each digit is encoded using a specific pattern of four bars. Note the thickness of each bar and group them into sets of four.
For example, if the first white bar after the start pattern is the thinnest, note it as 1. If the following black bar is the thinnest, note it as 1. If the next white bar is the third thickest, note it as 3; if the following black bar is the second thickest, note it as 2. You would write down “1132”.
Continue this process until you have six groups.
Next, decode the bars on the right side, starting with the first black bar after the middle pattern. Measure and note the thickness of each bar, grouping them into sets of four.
This side uses an inverse pattern compared to the left side. Therefore, each group will start with a black bar.
Continue until you have another six groups.
Translate the measured bar widths into digits using a specific pattern code. Here’s the code for converting bar widths into numbers:
The final digit in the UPC-A barcode is the check digit, which is used to verify the accuracy of the barcode. To calculate it.
For example, if the result of step 4 is 16, the check digit will be 10 – 6 = 4. This should match the 12th digit of the barcode.
Understanding how to read a barcode without a barcode scanner is a valuable skill that can be useful in various situations. Learning to identify barcode types, decode their structures, and interpret the encoded data provides insights into the information stored within these ubiquitous symbols.
Whether you are troubleshooting bar code errors, verifying product details, or simply expanding your technical knowledge, the ability to read bar codes without scanning technology is both practical and informative.
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