Age Calculator

How to use the age calculator

Enter your date of birth, and optionally change the “as of” date if you want to calculate your age on a date other than today. The calculator instantly shows your exact age in years, months and days, your total days, weeks and hours lived, the day of the week you were born on, and a countdown to your next birthday.

It's a small, simple tool, but a surprisingly common one to need — whether you're filling in a form that wants your exact age, settling a debate about who's older, or just curious how many days you've actually been alive.

How the calculation works

Working out an exact age isn't quite as simple as subtracting your birth year from the current year — that approach can be off by one, because it doesn't account for whether your birthday has happened yet this year. This calculator compares full calendar dates properly: it works out the difference in years, then adjusts the month and day count depending on whether your birth date has occurred yet in the current month and year, borrowing days and months correctly the same way you would with long subtraction.

For the total days, weeks and hours figures, the calculator counts every actual calendar day between your date of birth and the “as of” date, correctly including the extra day added in every leap year — rather than assuming every year has exactly 365 days, which would drift increasingly inaccurate the further back your birth date is.

Worked example

Someone born on 15 June 1990, checking their age on 25 July 2026, would be shown as 36 years, 1 month and 10 days old. That's a total of roughly 13,189 days, or about 1,884 weeks, since their birth — equivalent to just over 316,500 hours lived. Their next birthday, 15 June 2027, would be shown as a live countdown of days remaining.

Because 15 June 1990 falls before 25 July in the calendar year, the calculator correctly counts a full extra month into the age (June has already passed by July), which is exactly the kind of edge case that trips up a naive year-subtraction approach.

Why day of the week matters

The day of the week you were born on is determined purely by the calendar — it cycles in a fixed pattern based on the date, including how leap years shift the pattern slightly each year. It's a popular bit of trivia (there's an old rhyme, “Monday's child is fair of face...”, built entirely around it), and this calculator works it out instantly from your date of birth.

Practical uses for exact age

Beyond curiosity, knowing your precise age can matter for legal and administrative purposes — some forms, applications and eligibility checks ask for age in exact years and months, not just a birth date. It's also useful for working out someone's age on a specific past or future date, such as checking how old you'll be at retirement, or how old a family member was on a significant historical date.

Related calculators

If you're working out important dates for a pregnancy rather than a birthday, try our pregnancy due date calculator. For quick maths on percentages and proportions, see our percentage calculator.