Age Difference Calculator
The gap between two ages sounds simple, but stating it precisely in years, months and days takes more than subtracting birth years, because calendar months vary in length and leap days fall unevenly. This calculator handles all of that for you. You enter two dates of birth and it returns the exact age difference, broken down the way people actually say it: a whole number of years, then months, then the remaining days. The method is direct calendar date subtraction. Starting from the later birth date, it counts back the full years that fit, then the full calendar months, then the days that are left over, which is why a gap of a few months does not translate to a fixed day count. Because the result is the absolute difference, the order in which you enter the two dates does not matter; the tool always reports a positive gap from the earlier birth to the later one. Leap years are included automatically, since the calculation works with real dates rather than an assumed 365-day year. Every figure here is computed deterministically from the dates you enter, and the worked example below reconciles exactly to the calculator.
The age gap is the calendar difference between two birth dates, in years, months and days. Between 15 March 1990 and 20 July 1995 the difference is 5 years, 4 months and 5 days.
Age difference method
gap = | later date - earlier date |
years = full years between the dates
months = full months after the years
days = leftover days after the months
The difference is measured against the real calendar. Full years are counted first, then full months, then the remaining days, which naturally accounts for varying month lengths and for leap years.
Worked example
One person is born on 15 March 1990 and another on 20 July 1995.
- Count full years from 15 March 1990: to 15 March 1995 is 5 years
- Count full months from 15 March 1995: to 15 July 1995 is 4 months
- Count leftover days from 15 July 1995: to 20 July 1995 is 5 days
The age difference is 5 years, 4 months and 5 days. These are the calculator's default inputs, so the result above matches the widget exactly.
Age difference calculator: frequently asked questions
How do I calculate the age difference between two people?
Subtract the earlier date of birth from the later one, then express the gap in years, months and days. Start from the later date, count back full years, then full months, then the remaining days. From 15 March 1990 to 20 July 1995 the gap is 5 years, 4 months and 5 days.
Does the order of the two dates matter?
No. The calculator uses the absolute difference, so it does not matter which birth date you enter first. It always reports a positive gap between the two people, measured from the earlier birth to the later one.
Why is the month count sometimes uneven in days?
Calendar months have different lengths, from 28 to 31 days, so a gap of a few months does not convert to a fixed number of days. The calculator counts whole calendar months first and then the leftover days, which is how people normally state an age gap.
Does it account for leap years?
Yes. Because the calculation works directly with real calendar dates, leap days are included automatically wherever they fall between the two birth dates. You do not need to adjust anything for February 29.
Can I use this for any two dates, not just births?
Yes. Although it is framed around dates of birth, the same date subtraction works for any pair of dates, such as the gap between two anniversaries or two events. Enter the two dates and read off the years, months and days between them.
Official sources
- Civil date, time and calendar standards: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.