This age difference calculator works out the exact age gap between two people from their dates of birth. It shows the difference in years, months and days, plus total days and weeks, who is older, and how the ratio of their ages changes over time.
How the age gap is calculated
The calculator counts whole years, then whole months, then the remaining days from the older person’s birthday to the younger person’s. Leap years and different month lengths are taken into account, so the result matches a calendar count.
Worked example
Someone born on 15 April 1990 is 4 years, 6 months and 18 days older than someone born on 2 November 1994, a gap of 1,662 days.
The gap stays the same, the ratio does not
The age difference never changes, but the ratio does. When one sibling is 2 and the other is 6, one is three times as old. When they are 32 and 36, the older one is only about 1.1 times as old. That is why age gaps feel smaller as people get older.
Uses
- Comparing siblings, parents and children, or partners.
- Checking age gaps for family history and genealogy.
- Working out how old someone was when another person was born.
Frequently asked questions
Does the calculator handle leap years?
Yes. It uses calendar dates, so 29 February and leap years are counted correctly.
Does the order of the dates matter?
No. The calculator works out who is older and shows the difference either way.
Can I use it for things other than people?
Yes. It works for any two dates, such as the founding dates of two companies.
Is my data saved?
No. The calculation runs in your browser and nothing is stored.
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Last reviewed: October 2026. For information only; results are estimates; check important figures with a professional.