How it works
The age difference between two people is simply the time between their two birth dates. It never changes over their lives: if one person is 4 years and 3 months older today, they will be 4 years and 3 months older in 20 years too. The calculator counts complete years, then complete months, then the remaining days, the same way an exact age is calculated.
difference = later birth date − earlier birth dateWhen the day of the month of the younger person’s birthday is smaller than the older person’s, one month is borrowed using the length of the month before, so the result is always a real number of calendar days.
Worked example. Person A was born on 15 May 1990 and person B on 3 September 1994. From 15 May 1990 to 15 May 1994 is 4 years; to 15 August 1994 is 3 months; and from 15 August to 3 September is 19 days (August has 31 days). The age gap is 4 years, 3 months and 19 days — 1,572 days, or 224 weeks and 4 days. Person A is older.
Common uses
- Couples who are curious about their exact age gap.
- Siblings and twins — the gap between siblings, or confirming that twins born either side of midnight are one day apart.
- Forms and records that ask for the age difference between a parent and child or between spouses.
- Teams and classes — comparing the oldest and youngest members.
Age-gap rules of thumb
You may have heard the popular “half your age plus seven” rule for relationships. It is a social saying, not a scientific or legal standard, so this calculator simply reports the facts and leaves the judgement to you.
To find one person’s exact age today, use the age calculator. To convert a Hijri birth date first, use the Hijri converter.