Time & dates
Age calculator
Enter a date of birth, and optionally an 'as of' date, to get the exact age in years, months and days plus the running totals.
Leave the second date on today for a current age, or set it to any past or future date.
How exact age is counted
Age is the number of complete years, then months, then days between the date of birth and the chosen date. The calculator subtracts the three parts separately and borrows when a part goes negative, the same way you would subtract by hand. For a birth date of 15 March 1994 measured on 24 October 2026, the years are 2026 − 1994 = 32; from 15 March to 15 October is 7 whole months; and from 15 to 24 October is 9 days, giving 32 years, 7 months and 9 days. If the day of the month had not yet been reached, one month is borrowed and the days of the previous calendar month are added, so the count follows the real length of each month rather than a fixed 30.
The totals restate that same span in single units. Thirty-two years and seven months is 391 months; the day count divided by seven gives the whole weeks; and the raw day count is every midnight you have passed. Because months vary in length, a birthday is the only moment all three measures line up exactly.
| Milestone | Reached at about |
|---|---|
| 1,000 days old | 2 years 9 months |
| 10,000 days old | 27 years 4 months |
| 500 months old | 41 years 8 months |
| 20,000 days old | 54 years 9 months |
| 1 billion seconds old | about 31 years 8 months |
Reading the result
The years-months-days form is the one used on official documents and medical charts, so it is the answer to give when a form asks for exact age. The total-days figure is better for counting down to a milestone or comparing two people born days apart. One quirk to expect: someone born on 29 February has a true birthday only in leap years, so most calculators roll their non-leap-year birthday to either 28 February or 1 March, and the age still ticks over once a year. Set the second date to a point in the past or future to find an age on any day, such as a child's age at the start of a school term.
Frequently asked questions
How do I calculate age from a date of birth?
Subtract the birth year from the current year, then adjust down by one if the birthday has not happened yet this year. The calculator also fills in the exact months and days.
Why do the months and days not simply add up to the years?
Calendar months have 28 to 31 days, so months and days are counted against the real calendar rather than as fixed fractions of a year. Only on a birthday do all the parts reset together.
How is the age of a 29 February baby handled?
Their birthday falls only in leap years. In other years the age increases on 28 February or 1 March depending on the convention, so they still age one year at a time.