Age Difference Calculator
Work out the exact age gap between two people in years, months and days, plus total days and weeks, who is older and both ages on any date.
Enter two dates of birth to see exactly how far apart two people are in age: in years, months and days, and as total days, weeks and months. It answers the question siblings and couples ask, helps with age-band rules in youth sports, and is handy in family history when two birth dates are known. The gap itself never changes, so the calculator also shows both ages on any date you choose and a table of milestones.
How to use this tool
- Enter the first person’s date of birth.
- Enter the second person’s date of birth; the order does not matter.
- Optionally change the date on which both ages are shown.
- Read the gap, who is older and the milestone table.
Formula
Gap = whole calendar months from the earlier birth date to the later one (as years + months) + the days left over
Whole-month anniversaries are anchored to the earlier birth date without passing the later date, and the remaining days are counted exactly. Total days is the calendar difference, so it includes any 29 February in between. The decimal figure divides the leftover days by the length of the year they fall in.
Example
Person 1 was born on 12 March 1988 and Person 2 on 27 August 1993. Stepping 65 months forward from 12 March 1988 reaches 12 August 1993, and 15 more days reach 27 August, so the gap is 5 years, 5 months and 15 days. In days it is 1,994: 12 March 1988 to 12 March 1993 is 1,826 days because it includes 29 February 1992, and 12 March to 27 August adds 168. That equals 284 weeks and 6 days, or about 5.46 years.
Frequently asked questions
Why do our ages sometimes differ by 6 when the gap is 5 years and 5 months?
Ages are counted in completed years. Each year, between the older person’s birthday and the younger person’s birthday, the older one has already moved up a year, so the whole-number ages differ by one more than the whole years in the gap.
Does it matter which date I enter first?
No. The calculator always measures from the earlier date to the later one and tells you which person is older.
How are 29 February birthdays treated?
In common years 28 February counts as the anniversary, so 29 February 2000 and 28 February 2001 are exactly one year (365 days) apart.
Can I compare dates that are not birthdays?
Yes. Any two dates work, for example two wedding anniversaries or two company founding dates.
Last updated: 2026-10-30