Calculate an exact age down to the day
Whether you need your precise age for a form, want to know how many days old a milestone baby is, or are counting down to a birthday, this calculator works it out exactly — accounting properly for leap years and the different lengths of the months, which simple subtraction gets wrong.
How to use the age calculator
Enter a date of birth. Leave the "as of" date blank to calculate age today, or set it to any past or future date to find the age at that moment. The calculator returns years, months, and days, plus the total number of days lived and how long until the next birthday.
How the calculation handles the calendar
Rather than dividing total days by 365, the calculator counts complete years, then months, then the remaining days, borrowing from the previous month's true length when needed. This is why it can tell you that you are, say, 36 years, 6 months, and 24 days old rather than an approximate decimal.
Leap years and the 29 February question
People born on 29 February have a birthday only once every four years on the calendar, which the calculator handles correctly — in common years it treats the milestone appropriately rather than breaking. The leap-year rule itself is worth knowing: a year is a leap year if it is divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year but 1900 was not.