Age Calculator
Age is the number of complete years elapsed, which is not the same as subtracting birth year from current year. This calculator gets it right, including the months and days.
Formula
Age = years elapsed, less one if this year’s birthday has not arrived
- Counting whole months and days needs the same carry rule as subtraction
Born 15 June 1990, on 1 March 2026: 35 years, 8 months, 14 days
The Mistake Almost Everyone Makes
Subtracting the birth year alone is wrong for anyone whose birthday has not yet arrived this year.
Someone born on 14 November 1990 is 35 on 2 September 2026, not 36.
The correct method:
- Subtract the birth year from the current year.
- If this year’s birthday has not happened yet, subtract one.
Years, Months and Days
The finer breakdown borrows from the calendar. Subtract the day numbers; if the result is negative, borrow the length of the previous month and reduce the months by one. Repeat for months against years.
Because month lengths differ, an age of "3 months" can span 89 to 92 days depending on where in the year it falls.
Leap Day Birthdays
Anyone born on 29 February has a true birthday only every four years. In UK law, for the purpose of attaining a given age, they are generally treated as having their birthday on 1 March in non-leap years.
Quick Reference
| Age | Days | Weeks | Hours |
|---|---|---|---|
| 1 | 365 | 52 | 8,766 |
| 18 | 6,574 | 939 | 157,788 |
| 30 | 10,958 | 1,565 | 262,980 |
| 50 | 18,262 | 2,609 | 438,300 |
| 80 | 29,220 | 4,174 | 701,280 |
Frequently Asked Questions
- How do I calculate my exact age?
- Subtract the birth year from the current year, then subtract one more if this year’s birthday has not yet passed. The months and days follow by borrowing from the calendar.
- How is age counted for someone born on 29 February?
- In UK law they are generally treated as having their birthday on 1 March in years without a leap day, for the purpose of reaching a particular age.
- Why does my age in months look odd?
- Month lengths vary from 28 to 31 days, so a whole number of months covers a different number of days depending on the time of year.
- How many days have I been alive?
- The total day count includes every leap day since your birth, which is why it does not equal your age multiplied by 365.