How to use the age calculator
Pick a date of birth and, if you like, a second date to measure to. It's today by default, so you see the current age. Change it to find out how old someone was on a past date, such as a wedding or graduation, or how old they will be on a future one, such as a retirement date.
The result shows the age the way people normally say it, in completed years, plus the exact remainder in months and days. Below that are the same span in months, weeks, days and hours, the date of the next birthday and the weekday of the birth.
How age is calculated
Age = completed years + completed months + remaining days
The calculator counts whole calendar months from the date of birth up to the target date, then the leftover days. Twelve completed months make a year. Counting months on the calendar, rather than dividing days by 365.25, gives the answer people expect: someone born on 15 March turns one year older on every 15 March.
Worked example: someone born on 15 June 1995 is, on 1 January 2026, 30 years, 6 months and 17 days old. From 15 June 1995 to 15 June 2025 is 30 years; from 15 June to 15 December is 6 months; from 15 December to 1 January is 17 days. In total that's 11,158 days, and 15 June 1995 was a Thursday.
Birthdays on 29 February
People born on 29 February (leap day) only see their exact birthday once every four years. In other years, this calculator treats 28 February as the birthday, which is also how a whole number of years is added to 29 February elsewhere on the site. Some countries' laws use 1 March instead for legal age, so check local rules if it matters for a license or contract.
Age in different cultures
- International age (used here) starts at zero at birth and goes up by one on each birthday.
- East Asian age reckoning traditionally started at one at birth and added a year at Lunar New Year. South Korea officially switched to international age for legal purposes in 2023.
- Chinese zodiac animals follow the lunar year, which starts between 21 January and 20 February. If you were born in January or early February, your animal may be the previous year's, so the calculator shows both.
Frequently asked questions
How do I calculate my exact age?
Count the full years from your birth date to today, then the full months since your last birthday, then the days left over. The calculator above does this automatically and also shows the total in days, weeks and hours.
How many days old am I?
Subtract your date of birth from today's date in days. Someone born on 15 June 1995 was 11,158 days old on 1 January 2026. Enter your own birth date above to see your total.
What day of the week was I born?
The calculator shows it under "Born on a". For example, 15 June 1995 was a Thursday. The weekday is worked out from the Gregorian calendar, which repeats every 400 years.
How old will I be in a given year?
Change "Age on this date" to any future date. Your age in a given year is that year minus your birth year, less one if your birthday hasn't happened yet on that date.
Ages are calculated on the Gregorian calendar. For legal purposes, some countries count a 29 February birthday as 1 March in common years.