How to use the age difference calculator
- Enter two dates of birth. The order does not matter: the calculator works out who is older.
- Add names if you like. They only label the results, and they stay as Person A and Person B if you leave them empty.
The result shows the age gap in years, months and days, who is older, the same gap in total months, weeks and days, each person's age today, and how many years apart their ages are today. Copy result puts a short summary on your clipboard. Nothing you type is saved or sent.
How the age gap is worked out
The age difference is the time from the older person's birthday to the younger person's birthday. It never changes, however old the two people get. The calculator counts it the same way as an age: whole years, then whole months, then days.
| Step | From May 15, 1990 to | Count |
|---|---|---|
| Whole years | May 15, 1993 | 3 years |
| Whole months after that | July 15, 1993 | 2 months |
| Days left over | August 2, 1993 | 18 days |
So someone born on May 15, 1990 is 3 years, 2 months and 18 days older than someone born on August 2, 1993. The same gap is 38 months and 18 days, 167 weeks and 6 days, or 1,175 days, including the leap day on February 29, 1992.
How many years apart are you?
Unless two people were born on the same day of the year, the difference between their ages in whole years changes during the year. Between the older person's birthday and the younger person's birthday, the older one has already had a birthday that the younger one has not, so the ages are one year further apart.
For the two dates above, the gap is 3 years and a bit, and their ages in 2026 are:
| Date | Born May 15, 1990 | Born Aug 2, 1993 | Ages differ by |
|---|---|---|---|
| March 1, 2026 | 35 | 32 | 3 |
| June 1, 2026 | 36 | 32 | 4 |
| October 8, 2026 | 36 | 33 | 3 |
So "how many years apart" can honestly be 3 or 4 depending on the day you ask. The exact gap of 3 years, 2 months and 18 days is the answer that does not change. The calculator shows both: the exact gap, and how far apart the two ages are today.
Siblings, parents, couples and twins
- Siblings: the gap between brothers and sisters, and who is the eldest, when two birthdays are close.
- Parents and children: the age difference between a parent and a child is the parent's age on the day the child was born. A parent born on January 31, 1995 whose child was born on February 28, 2027 was 32 years and 1 month old at the birth.
- Couples and friends: the age difference calculator by birthday gives the exact gap, not just the difference in birth years.
- Twins born on different days: twins born either side of midnight on New Year's Eve, December 31, 2019 and January 1, 2020, are 1 day apart but have different birth years.
For one person's exact age, use the age calculator. For a plain count of days between any two dates, use the days between dates calculator.
February 29 and the ends of months
A month is counted when the older person's day of birth comes round again. When a month does not have that day, its last day stands in. That is why January 31, 1995 to February 28, 2027 is exactly 32 years and 1 month: February has no 31st. In the same way, February 28 stands in for February 29 in years that are not leap years.
Spreadsheets count these cases differently. Google says that in DATEDIF months and years are "only counted if they are equal to or go past the 'day'", so near the end of a month a spreadsheet can show a day or two more or less than this calculator.
Age difference in Excel or Google Sheets
Put the older person's date of birth in A2 and the younger person's in B2. These work in Excel and Google Sheets:
| To get | Formula |
|---|---|
| Whole years apart | =DATEDIF(A2,B2,"Y") |
| Months after the whole years | =DATEDIF(A2,B2,"YM") |
| Total months apart | =DATEDIF(A2,B2,"M") |
| Days apart | =B2-A2 |
The earlier date must come first: Microsoft says "If the start_date is greater than the end_date, the result will be #NUM!" Microsoft also warns that the "MD" unit for leftover days "may result in a negative number, a zero, or an inaccurate result", so check the days against this calculator.
Questions and answers
How do I calculate the age difference between two people?
Count from the earlier date of birth to the later one in whole years, then whole months, then days. Or enter both dates of birth above. May 15, 1990 and August 2, 1993 are 3 years, 2 months and 18 days apart.
How many years apart are we?
The exact gap is shown in years, months and days. The difference between your ages in whole years can be one more than the whole years in the gap for part of each year, between the older person's birthday and the younger person's birthday.
Does the order of the two dates matter?
No. The calculator always counts from the earlier date of birth to the later one and tells you who is older.
What if both people were born on the same day?
The gap is 0 days and the calculator says they were born on the same day. Twins born either side of midnight are 1 day apart.
Does the age gap change as people get older?
No. The gap between two dates of birth is fixed. Only the difference between the ages in whole years moves, by one, at different times of the year.
Sources
Checked on 8 October 2026. If a rule has changed, please tell us.