Online age calculator for your exact age

How to use the age calculator

1. Enter your Date of birth. The field takes a real calendar date from 0001-01-01 to 9999-12-31.
2. Check Age on. It starts at today's date on your device. Change it to calculate age on a past or future date, or select Use today to reset it.
3. If your date of birth is February 29, a Birthday in non-leap years menu appears. Choose February 28 or March 1 as your birthday in years without a February 29. The choice can change the age result and the next birthday date.
4. Select Calculate age. The result shows your age as years, months and days, your total calendar days, and the date of the birthday on or after the Age on date.
5. Select Copy report to copy the plain-text report, or Download text to save it as age-calculation.txt.

Reset clears the date of birth, restores the February 28 convention, and sets Age on back to today. Changing either date or the convention hides the previous result until you calculate again.

How the age is calculated

Age counts whole years to your last birthday on or before the Age on date, then 0 to 11 whole months from that birthday, then the remaining days. For a birth date of 1990-06-15 checked on 2026-09-22, that is 36 years, 3 months, 7 days, since the last birthday fell on 2026-06-15. Total calendar days counts each day after the date of birth, up to and including the Age on date.

If a month step lands on a day that month does not have, the calculator uses that month's last day instead. From 2025-01-31 to 2025-02-28, the step cannot reach day 31, so it stops at February 28: 0 years, 1 month, 0 days.

With the February 28 rule, a 2000-02-29 birth date checked on 2028-02-28, a leap year, reads 27 years, 11 months, 31 days, since February 28 comes one day before that year's February 29 birthday. The month count stops at 11, so the 31 remaining days span January 28 to February 28.

What the report includes

Before you calculate, the result area shows a short prompt to enter your dates; the age, the total calendar days, the next birthday line and the plain-text report only appear after a successful calculation. If a date is invalid, the calculator marks that field and shows the error message beside it instead of producing a report.

If the browser blocks clipboard access, Copy report selects the report text so you can copy it by hand.

Select Download text to save the report as age-calculation.txt. The report repeats the date of birth, the Age on date, the age, the total calendar days and the next birthday line, and it names the convention used: the proleptic Gregorian calendar, whole years to the chosen birthday, then whole months, then remaining days. For a February 29 birth date, the report also states which day the calculator used for a non-leap-year birthday, February 28 or March 1.

Limits

This calculator works out age from a date of birth only. It does not convert a birth date into another species' years, such as dog years. It does not estimate life expectancy or an age of death, and it has no rules for a benefit-eligibility age such as a retirement or pension date.

The tool takes one date of birth and one Age on date. It cannot compare two people's birth dates to find the age gap between them; use the date difference calculator for that, entering both birth dates.

The Age on date must be on or after the date of birth; an earlier Age on date is rejected as an error rather than shown as a negative age. Dates are compared using UTC internally, not your device's timezone, so the calendar day you type is the day used, with no shift near midnight.

Calculations use whole calendar days with no time of day, and this calculator does not determine legal age for any purpose.