How to Read a Barcode: Digits, Structure and Phone Scans
You can read a barcode two ways. A scanner or phone camera reads the bars automatically. You can also read the human-readable digits printed beneath them, which follow a fixed structure. Knowing how to read both helps you spot typos and confirm what you are looking at.
Read the digits on a UPC
A UPC-A has 12 digits. Take 036000291452:
| Digits | Part | Meaning |
|---|---|---|
| 0 | Number system | 0 means a regular product |
| 36000 | Company prefix | Identifies the brand owner, assigned by GS1 |
| 29145 | Item number | Chosen by the brand for this product |
| 2 | Check digit | Calculated from the other 11 digits |
The company prefix and item number together take ten digits, but where one ends and the other begins varies by company. You cannot tell the split from the number alone. You can look up the owner in GS1's database to see who registered the prefix.
The number system digit tells you the kind of item. Common values are 0, 1, 6, 7 and 8 for regular products, 2 for variable-weight goods such as meat and produce, 3 for drugs, 4 for store-internal use and 5 for coupons.
Read an EAN-13
An EAN-13 has 13 digits. The first two or three form a GS1 prefix that shows which national member organization issued the number, such as 978 or 979 for books. Then come the company and item numbers and a final check digit. The prefix is about where the number was issued, not where the product was made.
Check the check digit
To confirm a number is valid, add the odd-position digits (1, 3, 5, ...) and multiply by 3, add the even-position digits, and see if the total is a multiple of 10. For 036000291452 that gives 42 + 18 = 60, so it is valid. If your total is not a multiple of 10, there is a typo. The UPC barcode generator runs this check as you type.
Reading other barcodes
- Code 128 and Code 39 often show text under the bars that matches the encoded data exactly, which may include letters. See the Code 128 generator.
- ITF-14 shows 14 digits; the first is a packaging indicator, the next 12 are the item number, and the last is the check digit.
- QR codes and other 2D codes have no readable digits, so you must scan them. See QR code.
Scan a barcode with your phone
Modern phones can read most barcodes without an app.
- Open the camera app and point it at the code. QR codes are detected automatically on iPhone and most Android phones.
- For product barcodes (UPC and EAN), use an app such as Google Lens or a store's own scanner app, which looks up the product.
- Hold the phone steady 6 to 12 inches away. Let the autofocus settle.
- Avoid glare on glossy packaging by tilting the item.
- If it fails, try more light, clean the lens, or move closer.
A plain camera app often shows only a link for QR codes and may not decode a UPC. A dedicated scanner app or Google Lens reads UPC and EAN into digits and can show product matches.
If a barcode will not scan
Compare the printed digits to what the scanner returned. If they match but the product is wrong, the number may be assigned to something else. If the digits are wrong, the code is damaged or misprinted. Common causes are low contrast, a missing quiet zone and printing too small.
Check your own barcodes
Generate a code with Barcode Ready, print a test page and scan it with a phone before making a large run. The barcode is drawn in your browser, and the number you enter is never uploaded. Compare the scanned digits with what you typed. If both match and the check digit is valid, the barcode is ready.