Age Difference Calculator

The age gap between two people is the time between their birth dates. The person born first is older. Comparing the full dates tells you the difference in years, months and days.

For example, someone born on 15 June 2000 is 3 years, 3 months and 5 days older than someone born on 20 September 2003. Their birth dates are 1,192 days apart. That gap stays the same throughout their lives.

Count forward from the older person's birth date to the younger person's birth date. Here is the example broken down:

Swapping the order in which you enter the people does not change who is older or the size of the gap. It only reverses the direction of the comparison. An answer such as “A is 3 years, 3 months and 5 days older than B” makes both points clear.

You do not need birth times for a comparison of calendar dates. You would need them for a precise time difference between twins or other people born on the same day.

When someone says they are 26, they usually leave out the months and days since their birthday. Subtracting these whole-number ages can make the gap appear to change during the year.

For the two people in our example:

Their actual birth-date gap is still 3 years, 3 months and 5 days on both dates. One person has had a birthday between July and October. Comparing the birth dates avoids this apparent change.

If you only know the birth years, you can estimate the gap, but you cannot find it exactly.

For people born in 2000 and 2003, subtracting the years gives 3. Their actual gap could be as short as 2 years and 1 day, from 31 December 2000 to 1 January 2003. It could also be as long as 3 years, 11 months and 30 days, from 1 January 2000 to 31 December 2003.

Knowing that one person is 25 and the other is 28 has a similar limitation. Their birthdays may fall nearly a year apart within their birth years, so the exact gap need not be three years. If the information is approximate, describe the result as approximate too.

The calculation works the same way regardless of the relationship. For siblings, it shows how far apart the births were. For partners, it gives their age difference, without telling you whether the relationship is suitable or how it will turn out.

For a parent and child, the gap also tells you the parent's age when the child was born. A parent born on 15 June 1990 was 30 years, 3 months and 5 days old when a child was born on 20 September 2020.

If you want to know both people's ages on a wedding date or another event, calculate each age using that event date. Their ages will be different from today, but the gap between their births will be unchanged.

Years, months and days are easy to use in conversation. Total days are useful when you want to compare several gaps using the same unit. Dividing total days by 365 gives only an approximate number of years because some intervals include leap days.

Month endings can also affect a years-and-months breakdown. A comparison involving 31 January and the end of February needs a rule for handling the missing day. If two tools disagree, compare their total days and their month-end rules before deciding that a result is wrong.