Birth Date from Age Calculator

Calculate a date of birth from age

This date of birth calculator works backward from an exact age and a reference date to estimate when a person was born. Enter the age in years, months, and days, then choose the date on which that age was measured. The result gives the corresponding birth date.

How the birth date calculator works

The calculator subtracts the entered years, months, and days from the reference date in calendar order. It accounts for different month lengths and leap years, making it more reliable than converting an age into a fixed number of days.

How to use the DOB calculator

1. Enter the date when the person's age was recorded.
2. Enter the completed years, months, and days of age.
3. Select Calculate to find the estimated date of birth.

When is this calculator useful?

Use it to calculate a date of birth from age information shown in historical, medical, school, or family records. You can also change the reference date to find the birth date associated with an age measured in the past or future, rather than using today's date.

Can a birth date be found from age in years alone?

Not exactly. A whole-year age identifies a possible range of birth dates because it does not show how many months and days have passed since the last birthday. For a single estimated date, enter the complete age in years, months, and days together with the correct reference date.

Birth date calculator vs. age calculator

An age calculator starts with a known birthday and finds the age on another date. This birth date from age calculator performs the reverse calculation: it starts with a known age and reference date, then works backward to find the date of birth.