Age calculator
Calendar months vary in length, so a correct age calculation borrows days from the right month. This one does, and also gives the duration in several units.
- Full years
- 36
- In months
- 436
- In weeks
- 1,896
- In days
- 13,277
- In hours
- 318,648
- Day of the week born
- June 15, 1990
- Next birthday
- June 15, 2027
- Days until then
- 237 days
- Half birthday
- December 14, 2027
The formula
Subtract year, month and day separately. If the day is negative, borrow the number of days in the month before the end date; if the month is then negative, borrow twelve months from the year.
Worked example
From 15 June 1990 to 20 October 2026 is 36 years, 4 months and 5 days, or 13,276 days.
How to use it
- 1The second date defaults to today; change it for a date in the past or the future.
- 2Leap days are handled by the calendar itself, so 29 February works.
- 3For working days rather than calendar days, use the business days calculator.
Questions people ask
Why do other tools give a different number of months?
Some divide total days by 30.44. That is an average, not a calendar. Borrowing from the actual previous month is the convention administrations use.
How are leap-day birthdays handled?
In leap years the birthday falls on 29 February. In other years jurisdictions differ: England and Wales treat 1 March as the legal date, while many civil-law countries use 28 February. This calculator uses 28 February.
Last reviewed: 2026-10-20