Comments on: “Fascinating” ABA Routing Number Facts

By: Malika

Malika — Wed, 05 Nov 2008 08:58:30 +0000

Cool but does anyone know how to calculate the fraction form? Where do you get the city or state prefixes?

By: Jery Kilker

Jery Kilker — Thu, 25 Jan 2007 13:59:37 +0000

Checksums are used in other cases when it is critical to have accuracy. The 10 digit ISBNs (International Standard Book Number) identifying book titles use this. As I recall the general facts, the first group is the language (0=English); the next group is the publisher (I’m looking at a Penguin book=525); the third group is the individual unique title (Al Franken’s ‘Lies’ = 94764); the last group and single digit is the checksum (7). Sometines the groups are separated by hyphens, sometimes not. Ironically, I do not remember the formula for achieving the checksum! Perhaps someone can provide this?

By: Kevin

Kevin — Thu, 06 Apr 2006 19:38:45 +0000

A little more precise info about the checksum…

The 9th (last) digit of the 9-digit routing number is actually the “check digit”.

1. Take the first 8 digits and run the formula just as described in the article:

226070319:

(2 x 3) + (2 x 7) + (6 x 1) + (0 x 3) + (7 x 7) + (0 x 1) + (3 x 3) + (1 x 7) = 91

2. Divide that number by 10 and take the remainder (91 modulus 10, for math geeks) = 1

3. Subtract that remainder from 10. 10 – 1 = 9.

4. That should always equal the last digit, aka the check digit.

By: Todd Derscheid

Todd Derscheid — Wed, 29 Mar 2006 02:13:32 +0000

I hadn’t done that, but I have had to manually multiply out the individual characters of auto VINs to see if they’re actually valid or if our checksum routine was off.

By: Cap

Cap — Wed, 22 Mar 2006 23:32:35 +0000

hey wow, i didnt know about this checksum thing.

i dont know why but I just calculated my checking account’s routing number, just to see if it’s true. talk about productivity.

nice link Jay.

By: Jay

Jay — Wed, 22 Mar 2006 19:28:17 +0000

Credit cards also use checksums:

http://www.beachnet.com/~hstiles/cardtype.html

By: mapgirl

mapgirl — Wed, 22 Mar 2006 15:23:16 +0000

Neat! I guess that’s how websites know if you’ve keyed in something valid?

By: franky the fsa

franky the fsa — Wed, 22 Mar 2006 13:53:00 +0000

Checksum, nice.