How to use the age calculator
- Enter the Date of birth.
- Leave Age on as today, or pick another date to get the age on that day.
- Read the Age in years, months and days.
- Below it you get Total months, Total weeks, Total days, the weekday you were Born on, the Next birthday, the Days until next birthday, and the age you are Turning.
What it does and when to use it
Saying “I’m 36” is easy, but forms and rules often need more precision: the exact age on an exam’s cut-off date, whether a child is old enough to start school by 1 September, how many days old a baby is, or how long until a milestone birthday. The calculator answers all of these from two dates.
It is also a quick way to find the weekday you were born on, or to work out the age of a document, a building or a pet.
To count the time between any two dates, not just from a birth date, use the date difference calculator. To count down to a birthday or event, try days until, and the day of the week finder tells you the weekday of any date.
How it works
- Dates are converted to day numbers (days since 1 January 1970 in the Gregorian calendar) using whole-number arithmetic, without the browser’s clock or time zone.
- Total days = day number of “Age on” − day number of the birth date.
- Years, months, days: the largest whole number of months k such that birth date + k months is not after “Age on”, then the remaining days. When a month is too short, the date is clamped to its last day, so 31 January + 1 month is 28 February (or 29 in a leap year).
- Total weeks = total days ÷ 7, with the remainder shown in days.
- Next birthday is the next anniversary on or after “Age on”.
Worked examples
All results come from the calculator.
Born 15 May 1990, age on 2 October 2026. Age 36 years, 4 months, 17 days. That is 436 months, 1,898 weeks and 3 days, or 13,289 days. The person was born on a Tuesday, and the next birthday is Saturday, 15 May 2027, in 225 days, when they turn 37.
A leap-day birthday. Born 29 February 2000, age on 2 October 2026: 26 years, 7 months, 3 days. The next birthday is shown as Sunday, 28 February 2027, with a note about places that use 1 March.
A short month. Born 31 January 2026, age on 1 March 2026: 0 years, 1 month, 1 day, or 29 days. One month after 31 January is clamped to 28 February, and 1 March is one day later.
Limits and tips
- Birth time is ignored. Age is counted in whole days, which is what forms and laws normally use.
- Some countries count age differently, for example traditional East Asian age reckoning. This tool uses the international convention where you are 0 at birth.
- Dates before 1582 use the Gregorian calendar projected backwards, so historical dates recorded in the Julian calendar may differ.
- Nothing you enter is saved or sent anywhere.
Frequently asked questions
How is exact age calculated?
Can I find someone's age on a past or future date?
How are 29 February birthdays handled?
Why do total days and "years, months, days" not seem to match?
Does my time zone affect the answer?
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