Ahnentafel numbers are a precise number system that we use to number our direct ancestors on our pedigree chart. The word “ahnentafel” is a composite of the German words, ahnen meaning ancestor and tafel meaning table or list. The ahnentafel numbering system is also to compile ascendant genealogical research using the Sosa-Stradonitz System.
The method of determining the ahnentafel number of a direct ancestor is based on multiples of two. To begin we start with the base (first) individual of our pedigree chart (generally oneself) and assign the number 1. The father of the first individual (number 1) will be assigned the number 2 (multiply 1 by 2). His father (the paternal grandfather of number 1) will be 4 (multiply 2 by 2). The father of number 4 will be number 8 (multiply 4 by 2), etc. Therefore, the number of every father on your pedigree chart will be a multiple of 2 (an even number).
To determine the ahnentafel number of the man’s appropriate spouse (your direct ancestor), simply add 1 (one) to his ahnentafel number. The mother of the first individual on the pedigree chart will be 3 (the father’s number, 2, plus 1); her father will be number 6 (3 x 2),; and her mother will be number 7 (number of her father, 6, plus 1).
Let’s consider the pre-printed pedigree chart that may be downloaded as a PDF file (from Google Your Family Tree Dan Lynch
What follows are images of two pages of a pedigree chart illustrating appropriate ahnentafel numbers.
Chart 1: Numbers that have been added in “maroon” are the “chart” numbers. On this chart the ahnentafel numbers are already provided (individuals 1-15). I’ve added male and female silhouettes to reinforce the concept that the male ahnentafel numbers will be a multiple of two (even number) while the ahnentafel numbers of females will be odd numbers. The only exception is if the base (or first individual) is a male, in which case the ahnentafel number is 1 (one).
Chart no. 2 (two): Again the chart numbers are designated in maroon. Because the ahentafels are not the same as the printed numbers on the pre-printed chart, I’ve chosen to use green to show the appropriate ahentafel numbers.
© Linda Woodward Geiger. All Rights Reserved.
 A pedigree chart is a “schematic drawing of the bloodlines that connect you to each of your direct ancestors” [See Helen F.M. Leary, editor. North Carolina Research: Genealogy and Local History (Raleigh, North Carolina: North Carolina Genealogical Society, 1996), 604. Hereinafter cited as Leary, ed., North Carolina Research.]
 Leary, ed., North Carolina Research, 611–612.