Birth Year Calculator

Input age details from a document or interview to quickly estimate the individual’s year (and range) of birth.

Reference date

Use the date the age was recorded (e.g., census date).

Years

Months

Days

If you only know the age in years, set months and days to zero.

Reference date: 11/25/2025

Recorded age: 30 year(s), 0 month(s), 0 day(s)

Estimated birth year: 1995

Approximate birth date: 11/25/1995

Likely birth range: 11/26/1994 – 11/25/1995

Use the range when searching archives or verifying identities—ages in historical records are often rounded up or down.

How to Use This Calculator

Use the date when the age was recorded (census, medical visit, employment form).

If months/days are unknown, leave them at zero for an approximate result.

Use the estimated year (and range) to filter civil, parish, or immigration records.

Approximate Birth = Reference Date − (Years, Months, Days)

Birth Year = Year(Approximate Birth)

Birth Range = Between (Reference − (Years + 1) + 1 day) and Approximate Birth

Example: Age 42y 3m 10d on 2025-11-09 → Approx birth 1983-07-30 → Birth year 1983.

Many historical documents round ages to the nearest year; widen your search by ±1 year.
Consider delayed birth certificates or baptisms when verifying exact dates.
Use estimated birth ranges to triangulate identities across multiple records.
Store both the exact estimate and range in your genealogy software for transparency.

Convert decimals into months/days (0.5 years ≈ 6 months) before entry for better accuracy.

Rely on the birth range output; it captures the possible window the individual was born.

Yes—the subtraction uses JavaScript date arithmetic, which respects calendar variations.

Use the Birth From Death Date Calculator to subtract age from a death record.