Age Calculator
Enter a date of birth to get an exact age in years, months and days, the total in weeks and days, the weekday you were born on, and how long until the next birthday.
How it works
Age is counted the way people say it: whole years first, then the leftover whole months, then the remaining days. The calculator subtracts the calendar components in that order and borrows from the previous month when the day-of-month has not been reached yet — which is why the answer stays correct across months of different lengths.
Because it works on calendar dates rather than a fixed number of days per year, leap years are handled automatically. Everything is computed in your own time zone from your device clock.
The formula
Calendar age
years = Y₂ − Y₁, months = M₂ − M₁, days = D₂ − D₁
Borrow a month when days is negative, then borrow a year when months is negative.
Total days lived
days = calendar days between the two dates
Days until next birthday
days = next birthday − today
Worked examples
| Scenario | Working | Result |
|---|---|---|
| Born 14 March 2001, checked on 5 September 2026 | 2026 − 2001 = 25 years, then March → September = 5 months, 14th → 5th borrows a month | 25 years, 5 months, 22 days |
| Born 29 February 2004 | Non-leap years have no 29 February | The birthday is counted on 1 March in common years |
| Born today | 0 years, 0 months, 0 days | 0 — and 365 days to the next birthday |
When you'd use it
- Filling in forms that ask for an exact age
- Checking eligibility cut-offs for school, sport or licences
- Working out an age on a specific past or future date
- Counting down to a birthday
Common questions
How is age calculated exactly?
By calendar components, not by dividing days by 365. Years are subtracted first, then months, then days, borrowing where needed. This matches how age is recorded officially and handles leap years correctly.
What happens if I was born on 29 February?
In leap years your birthday falls on 29 February. In common years most jurisdictions treat 1 March as the day you turn a year older, and this calculator follows that convention.
Can I calculate my age on a date in the past or future?
Yes. Change the “age at date” field from today to any date you like, and everything recalculates against that date instead.
Is my date of birth sent anywhere?
No. The calculation runs entirely in your browser. Nothing you type is transmitted, logged or stored on a server.