# How to: Number an Ahnentafel

Hi, I’m Penny Stratton, Publishing Director
at NEHGS. In this video tutorial I’ll show you how to use genealogical numbering in an
Ahnentafel or ancestor table. Ahnentafel is German for ancestor table. It
begins at or near the present and moves back in time, often to the earliest known ancestor.
It uses a mathematical numbering system that allows readers to quickly find a direct line
of ancestry. Each person in an ahnentafel is numbered.
The subject of the ancestor table—let’s say it’s you—is number 1.
4 and 5; your mother’s are numbers 6 and 7; and so on. The father always has an even number
and the mother an odd number. Mathematically, you can find the parents of
someone by doubling a person’s number. To find the father you multiply a person’s
number by 2 and to find a person’s mother, you multiply the number by two and add one.
And to find someone’s child, you divide the father’s number by 2.
Let’s look at a published example: to find the parents of number 57, Rachel Welsh, I
multiply 57 times 2 to find her father’s number and multiply 57 by 2 and add 1 to find her
mother’s. I can then flip through the book until I find number 114, George Welsh, and
number 115, Nancy Cannon. Note that every number needs to be accounted
for. So even when names aren’t known, we give the numbers or a range of numbers—as you
see here for numbers 116 and 117. In a sense, you can think of the ancestor
table as a multigenerational chart turned sideways to read vertically. You’re going
back in your ancestry, generation by generation. I hope you’ve found this video helpful. For