Age Calculator

Exact age in years, months and days, and the next birthday.

About Age Calculator

An age calculator works out an exact age in years, months and days from a date of birth, on today or any date, plus the next birthday and the weekday of birth.

How to use

  1. Enter the date of birth. The age appears immediately, counted to today.
  2. Change the "Age on" date to see the age on a past or future date, for example an enrolment cut-off or a retirement date.
  3. Copy any row from the details list.

What it does

  • Counts full years first, then full months, then the remaining days, following the calendar. A birthday on the 31st falls on the last day of shorter months.
  • Shows the age as a total in months, weeks and days as well.
  • Finds the next birthday, its weekday, how many days away it is and the age reached. On a birthday it says "Today".
  • Reports the weekday of birth and whether the birth year was a leap year.
  • Shows an error if the date of birth is after the "Age on" date.

Example

Born 1990-07-15, on 2026-10-28
Age: 36 years, 3 months, 13 days
In days: 13,254 days
Next birthday: 2027-07-15 (Thursday), in 260 days, turning 37
Born on a: Sunday

Privacy

The dates are compared in the browser. No request is made, and nothing is stored.

Frequently asked questions

How is age calculated in years, months and days?
Count the full years from the birth date, then the full months after the last birthday, then the days left over. Born 15 July 1990 and counted on 28 October 2026 gives 36 years, 3 months and 13 days.
When does someone born on 29 February have a birthday?
In a common year there is no 29 February, so this tool uses 28 February. Legally it varies: England and Hong Kong treat 1 March as the birthday, while New Zealand and Taiwan use 28 February.
How many days old am I?
Multiply your age in full years by 365, add one for each leap day you have lived through and add the days since your last birthday. The "In days" row does this exactly.
What day of the week was I born on?
Enter your date of birth and read the "Born on a" row. The weekday repeats on the same date every 5, 6 or 11 years depending on where the leap years fall, so it cannot be worked out from the year alone.