UPC Check Digit Calculator
UPC-A check digit and full code.
What it does
UPC-A ends with a check digit that catches scans gone wrong. Odd positions triple while evens count singly, summing to a multiple of ten with the check included. The cola classic 03600029145 resolves to check two.
The tool above runs the rule. With 03600029145 the odds give 42 with evens 16, so the sum is 58 and the check is 2 for a full 036000291452. With 04210000526 the sum is 46 and the check is 4. Dashes strip first, so hyphenated pastes work.
Passing arithmetic never proves registration. Any eleven digits can checksum while belonging to no product, and ISBN uses the mirrored weight order. Catalogs check GS1 registries after the math.
This page handles UPC-A only. It does not validate EAN-13 extras, ISBN books, or barcodes beyond twelve digits. For selling, license prefixes with GS1.
How to use
- Type the first 11 UPC digits.
- Read the check digit first.
- Read the full 12 digit UPC.
- Read the sum for records.
- Validate printed barcodes against it.
- Register prefixes with GS1 separately.
Formula
- d1-11
- First 11 digits, dashes stripped.
- weights
- Odd positions times 3, evens times 1.
- check
- Appended 12th digit.
UPC-A mod 10 rule on the first 11 digits. At any non digit the page stops with a message. A passing check confirms arithmetic, never GS1 assignment.
Worked example
Example: UPC starting 03600029145
Defaults: 03600029145 (classic cola UPC without check). Dashes strip before math.
- Inputs: first 11 digits 03600029145.
- Odds (1st,3rd...): 0+6+0+2+1+5 is 14, times 3 is 42.
- Evens: 3+0+0+9+4 is 16.
- Sum: 42 plus 16 is 58.
- Check: (10 minus 8) mod 10 is 2, full 036000291452. Tool shows the same.
Reference table
| First 11 | Check | Full UPC |
|---|---|---|
| 03600029145 | 2 | 036000291452 |
| 04210000526 | 4 | 042100005264 |
| 12345678901 | 2 | 123456789012 |
| 00000000000 | 0 | 000000000000 |
| 12345678910 | 4 | 123456789104 |
Limits
- UPC-A only. EAN extras differ.
- Arithmetic only. No registry check.
- Digits only. Letters rejected.
- One code at a time.
Common mistakes
- Using ISBN 1/3 order on UPC.
- Counting positions from zero.
- Forgetting dashes strip (they do not matter).
- Reading pass as registered.
- Mixing UPC-E short codes.
Try it yourself
Quick checks. Answers sit tucked under each question.
First 11 digits 04210000526?
Odds 13 times 3 is 39 with evens 7, sum 46. Check is 4 with full 042100005264.
First 11 digits 12345678901?
Odds 26 times 3 is 78 with evens 20, sum 98. Check is 2 with full 123456789012.
Questions
How is the sum figured?
Odds times 3 plus evens. Here 58.
How is the check digit figured?
(10 minus sum mod 10) mod 10. Here 2.
What is the full UPC?
Append it to the 11. Here 036000291452.
Is this the ISBN rule?
No. UPC-A uses 3/1 weights unlike ISBN 1/3 order. This page does UPC only.
Can I paste with dashes?
Yes. Dashes strip first.
Does pass mean registered?
No. Arithmetic only, never registry assignment.