Check digit calculator: EAN, UPC, GTIN, SSCC, ISBN
Work out a check digit, or verify that a number is correct. The whole calculation is shown step by step, and it runs in your browser.
Qreska does not issue EAN numbers
Result
Check digit: 7
Complete number: 5901234123457
The calculation, step by step
Counting from the right, the digits are given alternating weights of 3 and 1. Each digit is multiplied by its weight and the products are added up. The check digit is whatever brings that sum up to a whole multiple of ten.
| Position | Digit | Weight | Product |
|---|---|---|---|
| 1 | 5 | × 1 | 5 |
| 2 | 9 | × 3 | 27 |
| 3 | 0 | × 1 | 0 |
| 4 | 1 | × 3 | 3 |
| 5 | 2 | × 1 | 2 |
| 6 | 3 | × 3 | 9 |
| 7 | 4 | × 1 | 4 |
| 8 | 1 | × 3 | 3 |
| 9 | 2 | × 1 | 2 |
| 10 | 3 | × 3 | 9 |
| 11 | 4 | × 1 | 4 |
| 12 | 5 | × 3 | 15 |
| Sum of the products | 83 | ||
- The products add up to 83.
- 83 divided by 10 leaves 3.
- The check digit brings the sum up to a whole multiple of 10. With a remainder of 3 it is 7.
What a check digit is
A check digit is the last digit of a number, worked out from the others. It says nothing about the product: its only job is to catch a mistake. It detects every single-digit error and most swaps of two neighbouring digits, so a scanner or a warehouse system rejects a mistyped number instead of accepting it as some other real product.
EAN-8, EAN-13, UPC-A, GTIN-14 and SSCC all use the same GS1 modulo 10 method and differ only in length. ISBN-13 is an EAN-13 with a 978 or 979 prefix, so it works the same way. The older ISBN-10 is the exception: it uses modulo 11, which is why it alone can have a check digit written as the letter X.
Frequently asked questions
How does the check digit differ from the rest of the number?
The other digits identify the company and the product; the check digit is derived from them and exists only to catch errors. You cannot choose it: for a given number exactly one value is correct.
Can I invent my own EAN, since the calculator will give me the check digit?
No. A correct check digit only means the number is well formed, not that it is yours. The company prefix is assigned by GS1, and without one your number may point at a product belonging to someone else. The calculator checks the arithmetic, not your right to the number.
Why does an ISBN-10 sometimes end in X?
ISBN-10 divides by 11, so the check digit can come out anywhere from 0 to 10. Ten will not fit in a single character, so it is written as X. This never happens in ISBN-13, where the divisor is 10.
The check digit is correct but a system still rejects the number. Why?
The check digit only says the number is well formed. A system may also require that the number exists in its database, is the right length for that field, or carries a particular prefix. It is also worth checking for an invisible space pasted in with the number.
Does the number I type go anywhere?
No. The whole calculation happens in your browser; the number is never sent or stored. Close the page and nothing of it remains.