Ancestor Count Calculator

Calculate the theoretical and adjusted number of ancestors across generations, accounting for pedigree collapse.

Generations Back

Pedigree Collapse Rate (%)

Known Ancestors

Tab to move between fields

Theoretical Ancestors

2,046

Adjusted (w/ Collapse)

1,724

Unknown Ancestors1,704

Tree Completeness1.2%

Collapse Significance Gen20

How to Use This Calculator

Enter the number of Generations Back you want to project (e.g., 5 generations = great-great-grandparents).
Enter the Pedigree Collapse Rate percentage to account for cousins marrying in earlier populations.
Enter the number of Known Ancestors in your current tree.
Review Theoretical vs Adjusted Ancestor Count to understand how pedigree collapse reduces the true number.
Check Tree Completeness percentage and Unknown Ancestors to prioritize your research gaps.

How the result changes with Generations Back

Generations Back: Number of generations to calculate (1 = parents, 10 ~ 300 years)
Pedigree Collapse Rate (%): Percentage of ancestors who appear more than once in your tree (common in small communities)
Known Ancestors: Number of ancestors you have identified in your family tree

Identify Input Parameters
Generations Back = 10, Pedigree Collapse Rate (%) = 5, Known Ancestors = 20 = 3 input(s) provided
Calculate Theoretical Ancestors
Theoretical Ancestors
2046 = 2046
Calculate Adjusted
Adjusted
1724 = 1724
Calculate Unknown Ancestors
Unknown Ancestors
1704 = 1704
Calculate Tree Completeness
Tree Completeness = min(100
1.2 = 1.2%

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