Generation Length Calculator
Calculate the average generation length in your family line and project ancestor birth years further back in time.
Inputs
Results
Avg Generation Length
30 years
Projected 5-Gen Ancestor Birth
1,630
vs. Historical Average5 years
Historical Era Code3
How to Use This Calculator
- Enter the Earliest Known Birth Year and Latest Birth Year across the family line.
- Enter the number of Generations Between those two birth years.
- Select the Line Type: paternal or maternal, as generation lengths differ between lines.
- Review Average Generation Length in years and how it compares to the historical average.
- Use Projected 5-Gen Ancestor Birth Year to estimate when to start searching for earlier records.
How the result changes with Latest Birth Year
| Latest Birth Year | Avg Generation Length | Projected 5-Gen Ancestor Birth |
|---|---|---|
| 1,823 | 6.1 years | 1,750 |
| 1,879 | 14.1 years | 1,710 |
| 1,946 | 23.7 years | 1,662 |
| 2,003 | 31.9 years | 1,621 |
What each input means
- Earliest Known Birth Year
- Birth year of your earliest known ancestor in this line
- Latest Birth Year
- Your birth year or the most recent descendant's birth year
- Generations Between
- Number of generations from earliest ancestor to latest person
- Line Type
- Maternal lines tend to have shorter generation lengths (~22 vs ~25 years)
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersEarliest Known Birth Year = 1780, Latest Birth Year = 1990, Generations Between = 7, Line Type = 0 = 4 input(s) provided
- Calculate Avg Generation LengthAvg Generation Length30 = 30
- Calculate Projected 5-Gen Ancestor BirthProjected 5-Gen Ancestor Birth1630 = 1630
- Calculate vs. Historical Averagevs. Historical Average5 = 5
- Calculate Historical Era Code3 = 3
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