Age Calculator

Calculate exact age in years, months and days, plus total days, hours and minutes.

What the Age Calculator does

Age is counted in whole calendar years, months and days rather than as a decimal. When the day of the month has not yet been reached, the calculation borrows days from the preceding month, which is exactly how people count age in conversation.

Formula

Years = Year difference, reduced by one if the birthday has not yet occurred
Months and days borrow from the previous period when negative
Total days = (End date − Start date) in whole days

Inputs explained

Input	Unit	Required	Notes
Date of birth	date	Yes	—
Age at date	date	Optional	Leave blank to use today.

How to use it

Enter Date of birth.
Optionally add Age at date.
Select Calculate.

Worked example

Someone born on 14 March 1990, measured on 14 August 2026.

Date of birth: 1990-03-14
Age at date: 2026-08-14

36 years, 5 months and 0 days — about 13,302 total days.

Reading the result

Age is reported as completed years, months and days — the convention used on official forms almost everywhere.
The months figure counts calendar months, not fixed 30-day blocks, so the same day count can produce different month totals depending on which months it spans.

Assumptions and limitations

Dates are treated in local time with no timezone conversion, so a birth date is the calendar date as written.
The Gregorian calendar is assumed throughout, including leap-year rules.

Common mistakes

Entering dates in the wrong order, which produces a negative or swapped span.
Expecting a 29 February birthday to fall on that date every year. Non-leap years are handled by convention, and jurisdictions differ on whether the legal date is 28 February or 1 March.

Frequently asked questions

How is age handled for someone born on 29 February?

In common years the anniversary is usually treated as 1 March for legal purposes, though conventions differ by country. This calculator rolls to the equivalent date in the following month.

Why does the month count sometimes look odd?

Months have different lengths, so borrowing days from a 28-day February gives a different result than from a 31-day January. This is standard calendar arithmetic.