How to Calculate the Check Digit of a Routing Number from an Illegible Check

If you ever happen to have a torn or battered check that you can’t make out the check-digit (last number) of the routing number for, there is a way to work it out. This number can be calculated and this article explains just how to do that.

If you have torn a check by mistake and are no longer being able to make out the check-digit (last number) of the routing number, chill! You do not have to panic. You can still calculate and find out the number. Well this article will explain how:


Get a scrap paper and a pen for working out the math.

Pen down the first eight digits of the routing number that you know already from reading the check. Make enough room in between each number. You will probably require a two digit number to write down for each column in the final sheet.

Write the numbers 371371371 directly below the other line, by keeping one number above each other. You must have two rows of numbers now.

Multiply the top number by the bottom number, for each column. Remember that you are not supposed to multiply the whole 8 digit number by the nine digit number. These columns are separate entries.

Write the answers to the products on a new line below. The last column is not very important because there is insufficient data to determine this number. You may just write down the ones-digit number of the product.

Add up the products together.

Round up the total of the products to the nearest ten. In case the sum is an exact figure that is evenly divisible by 10, you may exclude this step.

If the total is not exact, subtract the sum of the next highest multiple from the total to the addition of the products together. The result you get will be your check digit. But, if the total is an exact figure that is evenly divisible by ten, there will be no difference between the two. Hence, in that case your check digit number will be 0.


This kind of multiplication is commonly known as MOD-10. The reason being-most people don’t know the calculation by its real name. Before starting with the calculations make sure that the check isn’t ripped in a place where it could be easily traced. Unfold the rip and look at the routing number. You may not even need to perform any calculation at times.