Age Calculator

Checked 15 October 2026. What was checked. How these pages are maintained.

How age is counted

Age in years is how many birthdays have happened on or before the chosen date. Months and leftover days are counted from the last birthday-month. Leap-day birthdays are treated as February 28 in common years.

Worked example

Born 19 September 1990, on 19 September 2026 you turn 36 years 0 months 0 days. The day before, you are 35 years 11 months 30 days or 31 days depending on the month length.

Age in whole years is what most forms want. This page also shows leftover months and days. Time zones follow the browser clock, not the hospital’s.

Birthdays, then the leftover month

Someone born on 3 June 1988, measured on 30 September 2026, is 38 years, 3 months, and 27 days. The year count is how many birthdays have happened on or before 30 September. The 38th birthday was 3 June 2026. From 3 June to 3 September is 3 months. From 3 September to 30 September is 27 days. The day before the birthday, 2 June 2026, the year count is still 37. Forms that ask for age in whole years want 38 on 30 September and 37 on 2 June. The months and days are extra, for a form that asks for them.

The “age on this date” box is how you get a historical age instead of age today. Leave it on today for a current age. The total in days is the straight midnight-to-midnight count and will not match “years × 365” because of leap days.

29 February

A birthday on 29 February is treated as 28 February in a common year, which is what the date math does when February does not have a 29th. Time zones follow the computer’s calendar, not the hospital’s. Two sites that differ by one day are usually counting “today” in another zone or including an extra endpoint. This page uses the local dates you type and does not ask for a time of birth. It is also fine for a pet, a company, or a machine. It is not a legal determination of age for a licence or a benefit.

Common questions