How the age calculation works
Your "official" age is counted in completed years: you turn a year older only on your birthday, not before. This calculator does the same, but also adds the months and days elapsed since your last birthday, so you know exactly how much time has passed since you were born. For example, someone born on 15 March 1990 is, on 5 September 2026, 36 years, 5 months and 21 days old.
The "Age on" field defaults to today, but you can change it to find out how old you were (or will be) on any date: handy for forms, applications, enrolments and age limits.
What the numbers mean
- Years, months, days: completed years, whole months since the last birthday, and the remaining days.
- Total days: every day lived, leap years included. A 30-year-old has lived about 10,957 days.
- Total weeks and months: the same span expressed in whole weeks and completed months.
- Next birthday: how many days are left and what age you will turn.
Leap years and 29 February
The calculation accounts for leap years, so the total days are exact. People born on 29 February celebrate on 28 February in non-leap years; the countdown follows the same rule.
Frequently asked questions
How is exact age calculated?
Count the completed years, then the whole months since the last birthday, then the remaining days. The calculator does it automatically, taking month lengths and leap years into account.
How many days has an 18-year-old lived?
About 6,574 days (18 years × 365.25 days). Enter the date of birth to get the exact number.
Can I calculate age on a future date?
Yes: change the "Age on" field to the date you are interested in, such as an exam or a deadline.