Age Calculator

How old am I, exactly?

Enter your date of birth and this free age calculator from ÆON Toolhub answers in years, months, and days, then breaks the same span into months, weeks, days, hours, minutes, and seconds. Leave the second field on today and those smaller units tick upward live, so you can watch your age advance second by second.

By default it measures age as of today, but you can set any reference date to see how old someone was, or will be, on a specific day. Everything is calculated in your browser, so the date you enter stays private.

How do you use it?

Enter the date of birth. Use the first date field.

Choose the reference date if needed. The second field defaults to today. Change it to any past or future date to calculate age on that day. The live ticking only runs while the reference date is today, because a fixed past date has a fixed answer.

Read the results. The three big figures are the exact age in years, months, and days. Below them, the same age appears in six other units, and a line tells you how many days remain until the next birthday, which weekday it falls on, and which weekday you were born on.

Or work backwards. The reverse panel at the bottom turns an age into a birth year.

Why is exact age not simple subtraction?

Months have different lengths and some years have a leap day, so you cannot just subtract one date from another and divide. Doing it right means borrowing: if the day of the reference date is earlier in the month than the birth day, you take days from the previous month; if the month is earlier, you take a year. This calculator does that borrowing correctly, which is why the day and month figures are always accurate rather than rounded.

How do you find a birth year from an age?

You cannot pin it to a single year, and any tool that gives you one is guessing. Someone who is 30 today was born in one of two years, depending on whether their birthday has already passed. So the reverse panel shows the honest answer: the window of birth dates that produce that age on the reference date, plus both candidate years.

That is exactly what you need for a form, an eligibility check, or working out a birth year from a document that only lists an age.

What about leap years and February 29?

The maths uses the real calendar, so leap years are handled automatically. If the birth date is February 29, the age is still exact, and the next-birthday countdown points to the closest valid date in years that do not have a February 29. Most countries treat March 1 as the legal birthday in those years.

Does everyone count age the same way?

No, and it is worth knowing if you are comparing numbers with someone abroad. The figures here follow the international convention: you are zero at birth and turn one on your first birthday. Some East Asian traditions count differently, adding a year at birth or at the new year, so a traditional Korean or Chinese age can read one or two years higher than the number shown here.

Handy uses

• Personal: know your exact age, or a child's age in months for milestones.
• Forms and eligibility: check whether someone meets an age requirement on a given date.
• Planning: count the days to a birthday, or work out an age on a future event date.
• Records: confirm an age on a historical date, or recover a birth year from an age.

Your data stays private

The calculator runs entirely client-side. Your birth date is never uploaded, logged, or stored, and it clears when you close the tab. It also keeps working offline once the page has loaded.