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Age in Years Calculator

Created by Luciano Miño
Reviewed by Davide Borchia
Last updated: Jan 18, 2024

Our age in years calculator can find a person's age from their birthday and calculate the year they were born from their age!

Have you ever wondered how old someone is when they say they were born in 1989? Or did you try to guess someone's birth year from their age? With our calculator, you will be able to:

  • Calculate age from birth date;
  • Find birth year from age;
  • Learn how to calculate age; and
  • More about the date of birth calculation!

How to calculate age

Calculating someone's age might seem straightforward, but it can get a bit more technical depending on how precise you want to be.

If we assume every month to have exactly 31 days, then we can get someone's age in days with the following formula:

time = (years × 365) + (months × 31) + days

where years, months, and days are the differences between the person's birth date and current year, month, and day.

How do I calculate someone's age in years?

To calculate a person's age in years:

  1. Take the difference between the current year and their birth year: years = current year - birth year.
  2. Take the difference between the current month and their birth month: months = current month - birth month.
  3. Take the difference between the current day and their birth day: days = current day - birth day.
  4. Replace these differences in the age formula: age = (years × 365) + (months × 31) + days. This is the person's age in days.
  5. Divide the result by 365 to get the age in years.

Calculate age from birth date example

For example, if someone was born on July 4th, 1989 and today was July 5th, 2022 following the previous steps would result in:

  • Years difference: 2022 - 1989 = 33. Note that this is the person's age if the date we're comparing to was their current year's birthday.
  • The months difference is 0 in this example.
  • The days difference is: 5 - 4 = 1.
  • Putting every difference in the corresponding variable inside the age formula: time = (33 × 365) + (0 × 31) + 1.
  • As a result, we get that the person is approximately ≈ 12, 046 days old.
  • We can divide by 365 to get the number in years: 12, 046 / 365 = 33.0027 years

💡 Note that this is an approximation since we're not considering leap years. Our age in years calculator does include them in the calculation, and it can also output a person's age in many different units, such as: days, hours, minutes, and seconds!

Calculate date of birth

Our age in years calculator doesn't only calculate age by birth date. It can also work the other way around!

To calculate the date of birth, simply input the person's age in years, months, and days, and our tool will automatically find their date of birth!

Other useful tools

Feel free to check any of our age calculators if you enjoyed this age in years calculator:


How old is the oldest person ever?

122 years and 164 days. The oldest person whose age was verified is Jeanne Calment, who lived 122 years and 164 days from February 21st, 1875 to August 4th, 1997.

How old will I be in 2024 if I was born in 2002?

22 years old. If you were born in 2002 and wanted to find out how old you will be on your birthday in 2024, simply subtract your birth year from the year you're comparing to: 2024 - 2002 = 22.

Luciano Miño
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