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- Age difference is the time between two birth dates, shown in years, months and days.
- If you only know ages, the gap is the older age minus the younger age.
- The calculator also shows total months, weeks and days between the two dates.
- The half your age plus seven rule is a popular rule of thumb, not a law.
How to use the age difference calculator
Choose birth dates or ages
Birth dates give an exact gap. Ages give a gap in whole years.
Enter both people
Pick both dates of birth, or type both ages.
Read the gap
You see who is older, the gap in years, months and days, and the total in months, weeks and days.
Check the rule of thumb
The calculator also shows the half your age plus seven figure for the older person.
How age difference is calculated
Start with the earlier birth date. Count whole months forward until the next month would pass the later birth date, then count the remaining days. If a month is shorter than the starting day, the last day of that month is used, so January 31 plus one month is the end of February.
Age gap
Gap from ages = older age − younger age
Gap from dates = full years, months and days between the two birth dates
Total days = the number of days between the two dates
Leap days are included in the day count.
Half your age plus seven
Youngest suggested age = your age ÷ 2 + 7
Oldest suggested age = (your age − 7) × 2
This is a social guideline from popular culture. It has no legal or scientific basis.
Worked examples
Two birth dates
Person 1 was born on June 15, 1990 and person 2 on March 10, 1993.
June 15, 1990 plus 2 years 8 months is February 15, 1993, and 23 days later is March 10.
Two ages
One person is 35 and the other is 31.
With only ages, the exact months and days cannot be known.
A month end
Born on January 31, 2000 and March 1, 2000.
January 31 plus one month is February 29, 2000 (a leap year), and March 1 is one day later.
Half your age plus seven chart
Rule of thumb by age
Youngest and oldest suggested ages.
It is only a guideline, and personal and legal circumstances matter more.
Where an age difference calculator helps
Couples and families
Find the exact gap between partners, siblings or cousins.
Family trees and history
Work out the gap between relatives from their birth dates.
Settling a debate
Check who is older and by how many days.
Planning
Combine it with the date difference calculator for other date gaps.
The half your age plus seven idea is a social guideline, not a rule of law and not a measure of whether a relationship will work. Laws about age and consent are set locally and are separate from this calculator.
Age difference calculator FAQ
How do I calculate the age difference between two people?
Subtract the earlier birth date from the later one, counting years, then months, then days. With only ages, subtract the younger age from the older age.
Can I find the gap in months or days?
Yes. The result lists total months, weeks and days between the two birth dates.
What is the half your age plus seven rule?
It says the youngest age someone should date is half their own age plus 7. For a 30 year old that is 22. It is a casual rule of thumb only.
Does the calculator count leap years?
Yes. The day count uses real calendar dates, so leap days are included.
What if we were born on the same day?
The result is 0 days, and the calculator says you were born on the same day.
Why can the gap in years be different from the difference of birth years?
Birth years ignore the month and day. Someone born in December 1990 and someone born in January 1991 are one month apart even though their birth years differ by one.