Unlocking the Secret in Product Codes

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In this activity, learners will explore how product barcodes are scanned accurately and be able to "guess" the last number in a 13 digit barcode correctly every time. By using a simple formula, learners will recognize that the last number in a barcode, called a "checksum," is used by the computers scanning products to make sure that they read the code accurately. If the calculations do not match the checksum, then the machine will give an error detection code. This activity includes step-by-step instructions with photos, an explanation of the computer science behind the activity, printable poster showing calculations, and optional challenges.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$1 - $5 per group of students

Age Range:
Ages 6 - 14

Resource Type:


Materials List (per group of students)

  • Something to write with (pencil, pen, crayon, whiteboard marker, etc.)
  • Something to write on (paper, whiteboard, window, etc.)
  • A few household items with 12 or 13 digit product codes on them (canned food, stationery (e.g. notebook), a book with a 13-digit ISBN number on it


  • Engineering and Technology
    • Computing
      • Computer Science
  • Mathematics
    • Number and Operations
      • Multiples and Factors
      • Operations

Informal Categories

  • Computers


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access



Funding Sources:

  • Google
  • Microsoft