What is the moon phase today?
The moon goes through eight named phases as it orbits Earth, repeating every 29.53 days. That cycle is called the synodic month, and it is the basis for almost every lunar calendar in human history. The current phase, illumination percent, and moon age are shown in the visualizer panel above.
Illumination is the percent of the visible disk that is lit by the sun. A new moon is 0 percent lit and is essentially invisible from Earth. A full moon is 100 percent lit and rises around sunset. The first quarter and last quarter moons sit at 50 percent and are visible in the afternoon and predawn sky respectively.
The eight moon phases
The eight named phases are new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The waxing phases are when the illuminated area is growing from the right side in the northern hemisphere, and the waning phases are when it is shrinking toward the left. Gibbous means more than half lit but not yet full, and crescent means less than half lit but not yet new.
What was the moon phase on my birthday?
The birthday moon lookup lets you pick any date from 1900 to today and see the moon phase, illumination, and moon age for that day. The result is calculated the same way the current phase is calculated — from a known new moon reference and the synodic month.
How is the moon phase calculated?
The phase fraction is computed from a single reference new moon — January 6, 2000 at 18:14 UTC — and the 29.5306-day synodic month. For any date, the number of days since the reference is divided by the synodic month and the remainder is the phase fraction. A fraction near 0 means a new moon, 0.5 means full, and any value in between is one of the six intermediate phases.
When is the next full moon?
The next full moon and the next new moon are shown with a live countdown. Full moons and new moons each happen every 29.5 days, so the gap between them stays close to a lunar month. The closest of the two is highlighted at the top of the panel.