Age Difference Calculator: Compute the Age Gap

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Below is an age difference calculator. Enter the birth dates for two people, and we'll tell you their age difference in years and days. We'll also show you their respective ages today in years and days.

Age Difference Calculator

Using the Age Difference Calculator

To compute the distance in age between two birthdays, simply fill out the two input fields:

  • Birthday One: Enter the birthday of the first person
  • Birthday Two: Enter the second person's birthday

Once you're happy with the dates, hit the 'Calculate Age Difference' button. Then we'll run off and do the math for the next three fields.

  • Age Difference: We'll report back who is older and how much older they are
  • Person One Age: We report the first person's age in years and days
  • Person Two Age: The second person's age today in years and days
Age difference calculator screenshot for two
Picture of the age difference calculator comparing the ages of two people

How do you calculate the days?

We start counting on the day of the older person's birthday. We then count every day in between, but we don't count the day of the younger person's birthday.

Basically, if you enter birthdays within one day of each other, it will read as 1 day. If you enter the same birthdays it'll come back as 0 days.

How do leap years affect birthday calculations?

We do count leap years. If the difference in birthdays happens to cross over a February 29 (or more than one!) we will factor it into the calculations.

Of course, generally leap years are abstracted away in the year number, since a year can be 365 or 366 days. In that case the number of years will cover the leap year.

What if the second birthday is before the first birthday?

You don't need to enter the dates in any sort of order. If the second person has a birthday before the first, we'll factor it into the calculation (and check the screenshot).

Our Other Age Calculator, Plus Dates and Times

Fun, right? We've got a bunch of other time, date, and age calculators for you:

We have built many other finance and econ calculators over the years. Have fun!



PK started DQYDJ in 2009 to research and discuss finance and investing and help answer financial questions. He's expanded DQYDJ to build visualizations, calculators, and interactive tools.

PK lives in New Hampshire with his wife, kids, and dog.

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