Working out your age sounds trivial — just subtract the birth year from the current year. But an exact age in years, months, and days has to account for whether your birthday has already occurred this year, differing month lengths, and leap years, which is where manual calculation usually goes wrong.
The Basic Approach
Start with the difference in years between the two dates. Then check the month and day: if the current month/day is earlier in the calendar than the birth month/day, subtract one full year and instead count the remaining months and days from the birthday just before today.
A Worked Example
Someone born on 20 May 2000, checking their age on 13 August 2026: the year difference is 26. Since 13 August is after 20 May, no adjustment is needed — the age is 26 years, plus 2 months and 24 days past their last birthday (from 20 May to 13 August).
Why Leap Years Trip People Up
If someone was born on 29 February, their "birthday" doesn't exist in non-leap years, and hand calculations often mishandle this edge case, along with the varying number of days in each month (28 to 31) when counting the leftover days.
Skip the manual counting — enter your date of birth into our age calculator below for your exact age in years, months, and days instantly.