Age Calculator
Find your exact age in years, months, and days. Also shows total days lived, total weeks, and time until your next birthday.
Age
0 years
📐 Formula
Age in Years = Year(today) − Year(birth), adjusted if birthday has not yet occurred this year
Frequently Asked Questions
Subtract the birth year from the current year, then adjust based on whether the birthday has occurred yet this year. For exact age in months and days, also compare the birth month and day to today's date.
September 9 is statistically the most common birthday in the US, followed by other September dates. This reflects a peak in December conceptions. February 29 (leap day) is the rarest birthday.
Multiply your age in years by 365, add the days for each extra month, then add extra days. Alternatively, use this calculator — it calculates the exact number of days between your birth date and today.
How is Age Calculated Exactly?
Exact age calculation isn't as simple as subtracting years — it requires accounting for whether your birthday has passed yet this calendar year, and how many days remain in the current partial year. Our calculator works through four steps: year difference, month adjustment, day adjustment, and conversion to total days and weeks.
How to Calculate Age Manually
Subtract the birth year from the current year
If born in 1990 and the current year is 2025: 2025 − 1990 = 35 years (tentative).
Check if the birthday has occurred this year
If today is March 15 and the birthday is July 20, the birthday hasn't happened yet — subtract 1. Age = 34.
Calculate remaining months and days
Count full months elapsed since the last birthday, then remaining days.
Convert to total days
Multiply complete years by 365, add days for leap years, add partial year days.
How Many Days Old Am I?
The number of days you've been alive is surprisingly large. A 30-year-old has lived approximately 10,950 days (not counting leap years). At 50, that's around 18,250 days. This calculator computes the precise figure accounting for all leap years in your lifetime.
When is the Most Common Birthday?
Research on US birth data consistently shows September 9 as the most common birthday, followed closely by other mid-September dates. This reflects a peak in December conceptions — nine months before September. The rarest birthday is February 29 (leap day), occurring only once every four years.
Age Calculation Across Different Calendar Systems
This calculator uses the Gregorian calendar standard, which is the international civil calendar. In some East Asian cultures, a traditional system adds 1 year at birth (you're "1" when born) and adds another year at the start of the lunar new year. Korean age, for example, may be 1–2 years higher than Gregorian age. Our calculator uses the standard Western Gregorian method.