Enter two dates of birth to see exactly how far apart two people are, who is older, when one was twice the other's age, and the part of each year when they are a year further apart. Runs in your browser; nothing is stored.
Person 1
Person 2
Enter both dates of birth to see the gap.
The exact gap never changes. What changes is the whole number of years people say out loud. Take Rohan, born on 10 March 2010, and Meera, born on 1 August 2012. The gap is 2 years, 4 months and 22 days. In January 2027 Rohan is 16 and Meera is 14: two years apart. On 10 March Rohan turns 17 while Meera is still 14, so for the next 144 days they are three years apart. On 1 August Meera turns 15 and it is two again.
So the stretch runs from the older one's birthday to the day before the younger one's, and it is longer the further apart the two birthdays are in the calendar. If the younger one's birthday comes earlier in the year, it runs over New Year. If they share a birthday it never happens. If the gap is under a year, they are the same age for part of every year. The calculator shows the stretch happening now, or else the next one.
This is the gap children argue about. A brother who is “three years older” in spring and “two years older” in autumn is not making it up; that is the stretch above. Siblings born less than a year apart get to be the same age for a few weeks or months each year, which is usually a big deal to the younger one. The exact figure also makes a good opening line for a card; the lists of birthday wishes for a brother and for a sister have the rest.
Most couples know their age gap in years and not much more. The stretch settles the friendly argument about whether it is two years or three: both, depending on the month. The exact figure is also a small, specific detail for a partner's birthday message, which is more personal than any quote. There is no right or wrong gap; this page only does the arithmetic.
The gap between a parent and a child is the parent's age when the child was born, which is the first sentence of the result. The twice-the-age date is when the child reaches that same age: a parent who was 28 when the baby arrived is twice the child's age around the child's 28th birthday. Before that day the parent is more than twice as old; after it, less, and the ratio keeps shrinking towards one while the gap stays exactly the same. It works for grandparents too.
The button under the result opens the card creator for whoever has the next birthday, with their age and a message about the gap already filled in. Change any of it before you send it. If the two of you are a couple, an anniversary card works too. For one person's round numbers, such as the day they turn 10,000 days old, use the milestone calculator.
The total in days counts every 29 February between the two birth dates. The years, months and days are counted on the calendar, as on the age calculator. The twice-the-age date is worked out in days, so it is exact whatever leap years fall in between.
In years without a 29 February the birthday is counted on 28 February. That can make the stretch when they are a year further apart a day longer or shorter in a leap year, and the calculator says so. If one was born on 28 February and the other on 29 February, both birthdays fall on 28 February in most years, so the difference only moves on 28 February of a leap year.
If they were born on the same date, there is no gap and they are the same age every day. If they share the day and month but not the year, the gap is a whole number of years and it never changes during the year, because both ages go up on the same day.
Twins born at 23:55 on 30 June and 00:05 on 1 July are ten minutes apart but have different birth dates, so the calculator shows a gap of one day. On the older twin’s birthday that twin is a year older for one day; the rest of the year they are the same age. Twins either side of midnight on 31 December even have different birth years. If you would rather count them as the same age, enter the same date twice.
No. The calculation runs in your browser. Nothing is sent anywhere or stored, and the dates are not put in the page address.