Age Calculator

Calculate exact age in years, months, days, hours and more from a birth date.

Exact age
Next birthday
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Enter your birth date to see your next birthday
Life milestones
AgeDateWhen
Enter your birth date to see milestones
Fun facts
Dog years
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1 human yr \u2248 7 dog yrs
Cat years
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Rough conversion
Zodiac
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Chinese zodiac
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Calculation details

Years / months / days are computed by anchored subtraction: year and month are taken from the calendar difference, then days roll over from the previous month if the day-of-month of the as-of date is earlier than the birth day-of-month. This avoids floating-point month errors.

Total days = floor((asOf - birth) / 86400000) using local midnight for both dates.

Total months = years * 12 + months. Weeks = floor(totalDays / 7).

Hours / minutes / seconds are derived from total days and the current time-of-day.

Day of week uses the local calendar date of birth.

Common questions
How is age calculated in years, months, and days?
The calculator takes the calendar difference between your birth date and the as-of date. Years come first, then months, then the remaining days roll over from the previous month if needed. This matches how people say their age in everyday speech.
Can I find my age on a past or future date?
Yes. Change the "Age at date" field to any date you want. Use it to check how old you were when an event happened or how old you will be on a future milestone.
Why does the total number of days differ from years \u00d7 365?
Years are not exactly 365 days — a leap year has 366. The calculator counts every real calendar day between the two dates, including all leap days you have lived through.
Are dog and cat years accurate?
They use the popular rule-of-thumb (1 human year \u2248 7 dog years, \u2248 5 cat years). Veterinary charts are more nuanced, but these figures are fine for a quick estimate.
What time zone is used?
The calculator uses your device's local time. Both dates are compared at local midnight, so the result will match the dates you see on a paper calendar.

For informational purposes. All calculations run in your browser — nothing is sent anywhere.

This age calculator takes your date of birth and an as-of date, then returns your exact age as a calendar difference — for example, 32 years, 4 months, 12 days. It also reports the running totals: how many months, weeks, days, hours, minutes and seconds you have been alive.

Example. A person born on 15 March 1992 checking their age on 15 April 2026 will see 34 years, 1 month, 0 days, roughly 12,450 days and about 1.07 billion seconds. The calculator also shows the weekday of birth (Sunday), the date of the next birthday with its weekday, a countdown in days, a life-milestones table (18, 21, 25, 30, 40, 50, 60, 65, 70, 80, 90, 100) with calendar dates, plus dog years, cat years, western zodiac and Chinese zodiac. Change the as-of date to look up age on any past or future date.