How the full moons are counted
The Moon goes from full to full every 29.5 days on average, but the real gap varies between about 29.3 and 29.8 days because its orbit is an ellipse. So rather than dividing by an average, the calculator works out the exact moment of every full moon since you were born, using the formulas astronomers use to predict them, which are accurate to within a minute or two.
Full moons by age
There are 12 or 13 full moons in a year, about 12.37 on average.
| Age | Full moons, roughly |
|---|---|
| 1 | 12 or 13 |
| 10 | 123 or 124 |
| 18 | 222 or 223 |
| 21 | 259 or 260 |
| 30 | 371 or 372 |
| 40 | 494 or 495 |
| 50 | 618 or 619 |
| 60 | 742 or 743 |
| 70 | 865 or 866 |
| 80 | 989 or 990 |
Your 100th full moon comes at about 8 years old, your 500th at about 40 and a half, and your 1,000th at about 81.
Blue moons
A blue moon, in the everyday sense, is the second full moon in a single calendar month. Because the Moon's cycle is shorter than every month except February, it happens every two or three years. The calculator counts the blue moons of your life using the calendar where you are now.
Questions
Did I actually see them all?
Almost certainly not. Clouds, daylight and bedtime get in the way, and a full moon is often below the horizon at the exact moment it's full. This is the number of full moons that have happened in your lifetime, all of them visible from somewhere on Earth.
Why is the time different from my calendar?
A full moon is a single instant, when the Moon is exactly opposite the Sun. Times here are shown in your own time zone, so a full moon late at night in the UK can fall on the next day in Asia.
How old am I on the Moon?
The Moon doesn't orbit the Sun on its own, so the usual answer is the same as on Earth. For other worlds, try how old am I on Mars.
Is my birth date stored anywhere?
Only in your own browser, so you don't have to type it again on other pages of this site. It's never sent to us or anyone else.