How do I calculate the age difference between two people?

Enter both birth dates. The page compares the older and younger birthday and shows the exact gap in years, months, and days.

Does the page tell me who is older?

Yes. The result identifies the older birth date and the younger birth date before showing the gap.

Why is this better than subtracting the birth years?

Subtracting years alone ignores whether the month and day have already passed. A full calendar-date comparison gives the correct age gap.

Can I compare siblings or partners with this tool?

Yes. Any two birth dates can be compared, whether they belong to siblings, partners, classmates, teammates, or any other two people.

What if both people were born on the same day?

The page will return a zero age gap and mark that the birthdays are the same.

Does the result include total days apart?

Yes. In addition to years, months, and days, the result includes the total days, weeks, and months between the two birthdays.

Age Difference Calculator

Compare two birth dates and calculate the exact age gap between two people. See who is older, the difference in years, months, and days, and the total time between the two birthdays.

Enter two birth dates

Add both birth dates to compare the exact age gap. This page is built for sibling age gaps, partner age differences, and any other two-person age comparison.

First birth date

Enter the first person's full date of birth.

Second birth date

Enter the second person's full date of birth. The result will automatically identify who is older.

Calculations stay in your browser. If you copy the link, the selected birth dates are included in the URL.

The result refreshes as soon as either birth date changes, so you can compare multiple people without reloading.

Age difference result

See the exact age gap, total time between the two birth dates, and which person is older.

Add two birth dates to begin

As soon as both dates are valid, the page will show the exact age difference between them.

How this age difference calculator works

The page compares two birth dates, then measures the full calendar gap between the older and younger date. It returns completed years, remaining months and days, and the total number of months, weeks, and days between them.

1. Add both birth dates

Enter the two dates of birth you want to compare.

2. Let the page identify the older and younger date

The result automatically sorts the two dates so the gap is calculated in the correct direction.

3. Read the exact age gap

See the age difference in years, months, and days, plus total time apart and which birthday came first.

When an age difference calculator is useful

An age calculator answers how old one person is, while an age difference calculator answers how far apart two birthdays are.

This is useful for comparing siblings, partners, classmates, teammates, or any two people when the exact age gap matters.

Calendar-aware comparison is more accurate than rough year subtraction because it keeps the month and day difference intact.

The same result also shows total days, weeks, and months apart, which helps when the exact gap needs to be described in different formats.

References and public sources

These public references support comparing two birth dates as a full calendar gap, not just rough year subtraction.

CDC / NCHS - Age

Defines age as age at last birthday, which supports treating age-related calculations as calendar-based comparisons anchored to real dates.

NIST - Leap year and leap second

Explains leap-year rules that matter when one or both birth dates cross February 29 in calendar-aware comparisons.

timeanddate - Duration between two dates

Provides a public reference for expressing calendar date gaps across years, months, and days instead of using year-only subtraction.

Age difference calculator FAQ

How do I calculate the age difference between two people?: Enter both birth dates. The page compares the older and younger birthday and shows the exact gap in years, months, and days.
Does the page tell me who is older?: Yes. The result identifies the older birth date and the younger birth date before showing the gap.
Why is this better than subtracting the birth years?: Subtracting years alone ignores whether the month and day have already passed. A full calendar-date comparison gives the correct age gap.
Can I compare siblings or partners with this tool?: Yes. Any two birth dates can be compared, whether they belong to siblings, partners, classmates, teammates, or any other two people.
What if both people were born on the same day?: The page will return a zero age gap and mark that the birthdays are the same.
Does the result include total days apart?: Yes. In addition to years, months, and days, the result includes the total days, weeks, and months between the two birthdays.

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