Moon Phase Calculator
Find the approximate moon phase, illumination percentage and moon age for any date.
Waning Gibbous
70% illuminated
Moon age: 20.2 days
Estimates use average synodic-month math and may differ from precise ephemeris data by up to a day.
Enter any date to see the approximate lunar phase, its name, illumination percentage, and the moon's age in days since the last new moon. The estimate uses synodic-month math from a known reference new moon.
How to use
- Pick a date using the date field.
- See the moon phase name, emoji, illumination and age.
- Try different dates to track the lunar cycle.
Frequently asked questions
- How accurate is this calculator?
- It's accurate to within about a day, based on the average 29.53-day synodic month; it's a good approximation but not a substitute for precise astronomical ephemeris data.
- What does illumination percentage mean?
- It's the approximate fraction of the moon's visible disk that is lit by the sun, 0% at new moon and 100% at full moon.
- What is 'moon age'?
- The number of days elapsed since the most recent new moon, ranging from 0 to about 29.5 days.