How do I calculate my age from my date of birth?
download.fan · Updated
Short answer
Subtract your birth year from the current year, then subtract 1 if your birthday hasn't happened yet this year. Someone born on August 15, 1990 is 36 on November 4, 2026, because 2026 − 1990 = 36 and August 15 has already passed. For an exact answer, count the leftover months and days too: that person is 36 years, 2 months and 20 days old.
Step by step
Step 1: Subtract the years
Take the birth year from the current year: 2026 − 1990 = 36.
Step 2: Check the birthday
If this year's birthday is still to come, subtract 1. If it has passed or is today, keep the number.
Step 3: Count the complete months
Count whole months since your last birthday: August 15 to October 15 is 2 months.
Step 4: Count the remaining days
Count from there to today: October 15 to November 4 is 20 days.
What is the fastest way to calculate your age?
Enter your birth date in this age calculator to get your age in years, months and days. It handles leap years and months of different lengths from the actual calendar, and it also shows the weekday you were born on and how long it is until your next birthday.
Counting by hand is fine for whole years. It gets error-prone when you need months and days, because months run from 28 to 31 days.
How do I calculate age in Excel or Google Sheets?
With the birth date in cell A2, use =DATEDIF(A2,TODAY(),"Y") for complete years. Add =DATEDIF(A2,TODAY(),"YM") for the months since the last birthday.
Be careful with the days part. Microsoft recommends against the "MD" unit because it can return a negative, zero or inaccurate result. If the start date is later than the end date, DATEDIF returns #NUM!.
What if I was born on February 29?
You still age one year per year. In non-leap years, people usually celebrate on February 28 or March 1, and the legal date varies by country, so check local rules if it matters for something like a license.
Does every country count age the same way?
Most use the birthday method above. South Korea's traditional count started at 1 at birth and added a year every January 1, and a law scrapped the traditional methods in favor of the international system, which took effect in June 2023. You may still see the older count in family or cultural settings.