Free Calculator
Moon Phase Calculator
Find the Moon's phase, illumination, and sign for any date - past or future. No location needed: the moon phase is the same everywhere on Earth.
A moon phase calculator finds the lunar phase for a given date from the angle between the Sun and the Moon - New Moon at 0 degrees through Full Moon at 180 degrees - and reports how much of the disc is lit.
How a moon phase is calculated
The Moon's phase is set entirely by the angle between the Sun and the Moon as seen from Earth, called the elongation. When the Moon sits in the same direction as the Sun (0 degrees) its lit face turns away from us and we see a dark New Moon; when it sits opposite the Sun (180 degrees) the whole face is lit and we see a Full Moon. The illuminated fraction is (1 - cos(elongation)) / 2, and the Moon completes the full cycle in about 29.5 days. This calculator computes the Sun and Moon positions with public-domain Meeus algorithms and reads the phase straight from their separation.
Moon phase calculator FAQ
How do I find the moon phase on a date?
Pick any day, month, and year above (past or future) and calculate. You can optionally add an hour for extra precision, but it is not required - the moon phase changes slowly enough that the date alone gives an accurate result. The calculator returns the phase name, the illuminated percentage, the moon sign, and the lunar age.
Can I check the moon phase for a future date?
Yes. The calculator works for future dates as well as past ones, so you can plan around an upcoming Full Moon or New Moon - useful for events, rituals, or simply curiosity. Astronomical accuracy is best within the years 1900 to 2100.
Why don't I need my location or time zone?
The Moon's phase is global. The illuminated fraction of the disc is the same from every point on Earth at a given instant, so unlike a birth chart, a moon phase calculation does not depend on your location or time zone at day granularity. We default the time to midday UTC when you do not enter an hour.
What are the 8 moon phases?
New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent. The cycle runs about 29.5 days from one New Moon to the next, the lit fraction growing (waxing) to the Full Moon then shrinking (waning) back to dark.
How accurate is this moon phase calculator?
It uses public-domain Meeus astronomical algorithms to compute the Sun and Moon positions, then derives the phase from their angular separation. The phase name and illumination are reliable for the modern era; results are most precise within the years 1900 to 2100.