How to Calculate Your Exact Age (Years, Months & Days)

Working out an exact age sounds trivial — just subtract the birth year, right? But getting years, months and days correct means handling leap years and the fact that months have different lengths. Here's how it's actually done.

The right method

To find age from a birth date to a target date (usually today), subtract in stages, borrowing when needed:

1. Days: target day − birth day. If negative, borrow a month (add the number of days in the previous month) and reduce months by one.
2. Months: target month − birth month (after any borrow). If negative, borrow a year (add 12) and reduce years by one.
3. Years: target year − birth year (after any borrow).

Worked example

Born 15 Aug 1990, today 5 Jun 2026:

• Days: 5 − 15 = −10 → borrow May's 31 days → 5 + 31 − 15 = 21 days, months −1.
• Months: 6 − 8 − 1 = −3 → borrow a year → 6 − 8 − 1 + 12 = 9 months, years −1.
• Years: 2026 − 1990 − 1 = 35.

Result: 35 years, 9 months, 21 days.

Why simple subtraction fails

Just doing 2026 − 1990 = 36 ignores that the birthday this year hasn't happened yet. And counting total days then dividing by 365 drifts off because of leap years (every 4 years adds a day). A correct calculator accounts for both.

Leap years

A year is a leap year if divisible by 4 — except century years, which must be divisible by 400 (so 2000 was a leap year, 1900 wasn't). This matters for Feb 29 birthdays and for accurate day totals.

Let the tool do it

Our age calculator handles all of this automatically — enter a birth date and get exact years, months and days, plus totals in weeks, days, hours and minutes, and a countdown to the next birthday. You can also set the "age at" date to any past or future day.

FAQ