Age Calculator

Enter your date of birth and the calculator works out your exact age in years, months and days, plus the running totals you rarely think about: total days alive, total weeks, days until your next birthday, and the day of the week you were born on. It also pins down your zodiac sign, Chinese zodiac animal, and which generation you fall into.

The maths is straightforward arithmetic against today's date. The interesting parts are the fiddly bits: an age of '34 years and 0 days' means today is your birthday; '34 years and 364 days' means it's the day before. The calculator handles the awkward case where your birthday hasn't happened yet this year by rolling back one year and counting forward through the months.

The total-days figure is computed from the actual elapsed milliseconds between your birthday and now, so leap years are handled automatically. If you are 30 years old, you have lived through 7 or 8 February 29ths depending on when you were born, and those extra days are baked into the total. The Gregorian rule, in place since Pope Gregory XIII's reform in 1582, says a year is a leap year if it's divisible by 4, except century years, except century years divisible by 400. So 2000 was a leap year, 2100 won't be.

Filling in forms is the most common one, especially the kind that ask for age in years and months rather than just years. Pension and benefit applications often need this. Parents track baby ages in weeks for the first year and months for the second, then quietly switch to years when nobody's checking. People also use the tool to count 10,000-day milestones (about 27 years and 4 months), or to plan birthday surprises by counting backwards from a target date.

If you're working out the age of someone else, like a child or a relative, just enter their date of birth instead of yours. For more detailed date arithmetic, the [Date Difference Calculator](/date-difference-calculator) works out the gap between any two dates, including business days only.