Age calculator
Work out an exact age in years, months and days from a date of birth, plus total days and weeks and the time until the next birthday.
Runs in your browser
How the age is worked out
Age is counted in birthdays, not in elapsed time. The calculator subtracts the calendar date of birth from the target date, borrowing from the real length of each month rather than an average — so someone born on 31 January is 1 month old on 28 February, and 1 month and 3 days old on 3 March.
The total days figure is a plain count of calendar days, unaffected by daylight saving: a day is a day whether it contained 23 hours or 25.
29 February
A leap-day birthday has no anniversary in three years out of four. This calculator follows the convention most jurisdictions use for legal age and treats 1 March as the anniversary in a common year, so a leap-day birth reaches each age on the same day everyone else born that year does.
East Asian age reckoning
The result above is the international count. Traditional East Asian reckoning starts a newborn at 1 and adds a year at Lunar New Year, which makes a person one or two years older than their international age.
That system is now largely historical for official purposes: South Korea moved to international age in June 2023, and Taiwan, Hong Kong and mainland China already use it in law and administration. It still appears in conversation and in fortune-telling, which is why the two numbers sometimes disagree.
Your data stays here
The arithmetic happens in your browser. The date you enter is not sent anywhere and is not stored.