How to Calculate the Age Difference Between Two People
Enter both dates of birth above to get the exact age gap — in years and months — between any two people, plus a check against the internet's 'half your age plus 7' dating-age rule.
The Formula
An age gap between dates of birth is simply the difference between the two dates, calculated the same way as a normal age calculation: subtract the earlier date of birth from the later one, borrowing across months and years as needed. Because both dates are fixed, the gap stays constant for life.
Common Uses
Checking the gap between siblings, partners, or family members; verifying the 'half your age plus 7' social rule for a relationship; genealogy and family-tree research; or simple curiosity about a celebrity couple's age difference.
Frequently Asked Questions
Q: How do I calculate age difference between two people?
A: Enter both dates of birth into the calculator above. It subtracts the earlier date of birth from the later one to give the exact gap in years and months.
Q: What is the 'half your age plus 7' rule?
A: A popular informal dating rule stating the youngest socially-acceptable partner age is half the older person's age, plus seven years. The calculator above checks your result against it automatically.
Q: Does the age gap between two people change over time?
A: No — the gap in years and months stays essentially constant for both people's entire lives.
Q: Can I calculate an age gap for people who have passed away?
A: Yes, the calculation only needs both dates of birth, so it works equally well for historical or genealogical research.
Q: What's an 'Irish twin'?
A: An informal term for siblings born less than twelve months apart, meaning the older sibling isn't yet one year old when the younger one arrives.