ISBN-10 vs. ISBN-13 comparison

Feature	ISBN-10	ISBN-13
Length	10 digits	13 digits
Check digit range	0–9 or X (=10)	0–9
Check algorithm	Alternating ×1–×10, mod 11	Alternating ×1/×3, mod 10
Prefix	None	978 (or 979)
Used since	1970	2007 (global standard)
Conversion	Add 978 prefix, recalculate check digit	979-prefix books have no ISBN-10

Check digit formula

ISBN-10: Multiply each digit by its position weight (10 down to 2 for digits 1–9), add them, the check digit is chosen so the total is divisible by 11. The formula:

sum = d₁×10 + d₂×9 + … + d₉×2; check = (11 − (sum mod 11)) mod 11

If the result is 10, the check digit is X.

ISBN-13: Alternating weights of 1 and 3 applied to all 13 digits; valid if the sum is divisible by 10:

sum = d₁×1 + d₂×3 + d₃×1 + … + d₁₂×3; check = (10 − (sum mod 10)) mod 10

GS1 prefix meaning

All ISBN-13 numbers use GS1 prefixes 978 or 979, which identify the product as a book under the Bookland EAN system. The 979 prefix was introduced to expand the ISBN namespace as the 978 block fills up. Notably, the 979-10 range is allocated to France's AFNIL agency (the French national bibliography), and 979-8 is used by Amazon for self-published books. ISBN-13 numbers beginning with 979 have no ISBN-10 equivalent.

ISBN Validator

Enter any ISBN-10 or ISBN-13 number (with or without hyphens) to verify the checksum and see the equivalent format. Hyphens and spaces are stripped automatically.

ISBN-10

ISBN-10 is a 10-digit number. The last digit (the check digit) can be 0–9 or X (representing 10). The check digit is computed so that the sum 10×d₁ + 9×d₂ + … + 1×d₁₀ is divisible by 11.

ISBN-13

ISBN-13 is a 13-digit number using the EAN-13 format. It begins with 978 or 979. The check digit is computed using alternating weights of 1 and 3.

Conversion

All ISBN-10 numbers have an ISBN-13 equivalent (prefixed with 978). ISBN-13 numbers starting with 979 have no ISBN-10 equivalent.