EAN 13 check digit and ISBN validator
Check the check digit of EAN-13 barcodes and ISBNs, work out a missing one and convert ISBN-10 to ISBN-13 and back, all in your browser.
One per line, up to 1000. With 12 or 9 digits the missing check digit is worked out.
Type an EAN-13 (13 digits) or an ISBN-10 (10 characters).
How it works
EAN-13 and ISBN-13
EAN-13 is the barcode on almost every product: 12 digits and a check digit. The check comes from multiplying the digits by 1 and 3 alternately, from left to right, and taking what is missing to reach the next multiple of ten. Since 2007 books use the same format with the prefix 978 or 979: an ISBN-13 is an EAN-13. The first digits hint at the origin: 84 is assigned in Spain, 977 to magazines and newspapers, and 20 to 29 are kept for in-store use.
ISBN-10 and conversion
Before 2007 the ISBN had 10 characters and a different formula: weights from 10 to 2 and a remainder modulo 11, so the check can be 10 and is written X (080442957X). To turn an ISBN-10 into 13 digits, put 978 in front, drop the old check and compute the new one; the reverse only works with the 978 prefix, because 979 numbers were born with 13 digits.
If the last digit is missing, type 12 or 9 digits and the tool works it out. It does not add the hyphens between ISBN groups: that needs the range table of the International ISBN Agency.