How do I calculate my exact age in years, months, and days?

Count the whole calendar months from your date of birth to today, then the days since the last monthly anniversary. Every 12 whole months make a year. When a month has no matching day, such as the 31st in a 30-day month, its last day counts as the anniversary.

Why does my age sometimes show 0 months?

In the month after your birthday the months figure is 0, because less than one whole month has passed since your age in years went up.

What day of the week was I born?

The calculator shows the day of the week for your date of birth alongside your age results.

Is this calculator accurate for all dates?

It follows the Gregorian calendar for any past date the date picker accepts. It counts whole calendar months, then days, so leap years and months of different lengths are handled, and for birthdays on the 29th, 30th or 31st the last day of a shorter month counts as the monthly anniversary.

Age Calculator from Birthday

Enter your date of birth to calculate your exact age in years, months, and days. The calculator also shows the date of your next birthday and how many days away it is. Everything runs locally in your browser.

Date of birth

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How it works

The calculator uses JavaScript's built-in Date object to find the difference between your date of birth and today. It counts complete years first, then remaining months, then remaining days, correctly handling leap years and months of different lengths. Total days are the number of calendar days between the two dates.

Processing runs in your browser

All calculations are pure JavaScript running in your browser tab. Your date of birth is not sent to our servers, stored, or logged at any point.

Related operations

To work out days between any two dates, use the date calculator. For converting between Unix timestamps and human dates, try Unix timestamp. To convert times across zones, see the timezone converter.

Frequently asked questions

How do I calculate my exact age in years, months, and days?: Count the whole calendar months from your date of birth to today, then the days since the last monthly anniversary. Every 12 whole months make a year. When a month has no matching day, such as the 31st in a 30-day month, its last day counts as the anniversary.
Why does my age sometimes show 0 months?: In the month after your birthday the months figure is 0, because less than one whole month has passed since your age in years went up.
What day of the week was I born?: The calculator shows the day of the week for your date of birth alongside your age results.
Is this calculator accurate for all dates?: It follows the Gregorian calendar for any past date the date picker accepts. It counts whole calendar months, then days, so leap years and months of different lengths are handled, and for birthdays on the 29th, 30th or 31st the last day of a shorter month counts as the monthly anniversary.

Last reviewed September 30, 2026

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