Genealogy & Family

Ahnentafel number

Father, mother and generation of an Ahnentafel number.

  • Instant
  • Free
  • Private (processed locally)
  • No sign-up

ℹ️ Ahnentafel (Sosa-Stradonitz) system: the starting person is no. 1; the father of individual n is 2n, the mother 2n+1. Men have an even number, women an odd number (except no. 1). 100% local.

Explore an Ahnentafel number

Enter an Ahnentafel number: the tool shows the generation, the father, mother and child numbers.

Example

InputValue
Number5
Father (2n)10
Mother (2n+1)11
Child (n/2)2
Generation3

100% local calculation.

Frequently asked questions

How does Ahnentafel numbering work?

The reference person is no. 1; the father of individual n is 2n, the mother 2n+1.

Men and women?

Men always have an even number, women an odd number, except no. 1.

What is the generation for?

It shows the ancestry rank: 1 = self, 2 = parents, 3 = grandparents, etc.