Age Calculator

What your result means

Your age is the number of whole years, months and days since you were born. Because months have 28 to 31 days, the calculator counts whole calendar months first and then the days left over, the way people count birthdays, rather than dividing a number of days by an average month. The same age is also shown in months, weeks, days and hours, with the weekday you were born and your next birthday.

How to use the Age Calculator

1. Enter your date of birth.
2. Leave “Age on” as today, or pick any past or future date, such as a test date.
3. Read your age in years, months and days, the same age in months, weeks, days and hours, your next birthday and your next milestones.
4. To work backwards, choose “Find birth date” and enter an age and the date it applies to.

Formula and worked example

age (years, months) = the most whole calendar months from the birth date that fit before the "age on" dateage (days) = days from that month-anniversary to the "age on" dateadding a month keeps the day of the month, or the last day of a shorter month (Jan 31 + 1 month = Feb 28 or 29)age in days = days between the two dates, counting every February 29 in betweenleap year: divisible by 4, except century years, which must be divisible by 400 (2000 yes, 1900 no)

Worked example: born Tuesday, May 15, 1990, age on Sunday, October 18, 2026. 36 whole years and 5 whole months after the birth date is Thursday, October 15, 2026; from there to Sunday, October 18, 2026 is 3 days. So the age is 36 years, 5 months, 3 days, which is 13,305 days or 1,900 weeks and 5 days. They were born on a Tuesday.

Birthdays on February 29

A February 29 birthday only falls every four years (2000 was a leap year; 1900 was not). This calculator uses one rule for every date: adding a year keeps the day, or the last day of a shorter month. So someone born on February 29, 2000 is 26 years, 11 months, 29 days on February 27, 2027 and 27 years, 0 months, 0 days on February 28, 2027. If a legal age depends on it, check which day the rule you are under uses: February 28 or March 1.

Chronological age on a test date

Teachers, speech and language therapists and psychologists often need a child’s exact age on the day of a test. Enter the date of birth, then the test date in “Age on”. The result gives years, months and days, and the short form years;months (for example 6;4 for 6 years and 4 months). Standardised tests differ on whether to round the days, so follow the rule in the test’s own manual.

Finding a date of birth from an age

Choose “Find birth date”, enter the age in years, months and days and the date it applies to. The calculator counts back whole months first, then days. Because months differ in length, near the end of a month up to three birth dates can share an age: on Tuesday, February 29, 2000, people born on January 29, 30 and 31, 2000 are all exactly 0 years, 1 month, 0 days old. The calculator gives the date with the same day of the month.

How old are you if you were born in a given year (as of Oct 24, 2026)

Your exact age depends on the day: enter your date of birth above for years, months and days.

Life milestones in days, weeks and months

Years use the Gregorian average of 365.2425 days. A billion seconds is 11,574 days, 1 hour, 46 minutes and 40 seconds.

Assumptions and limits

• Dates use the Gregorian calendar, the one used for civil dates almost everywhere today.
• The age counts whole days. Hours, minutes and seconds assume a birth time of midnight; for an exact birth time the figures can differ by up to a day.
• Some cultures count age differently, for example counting the year of birth as 1. This calculator gives age as most countries count it: 0 at birth, plus 1 on each birthday.

Frequently asked questions

Similar time & date calculators

• Day Counter

More free calculators

• Gold Calculator
• Gravel Calculator
• Solar Panel Calculator