Moon Phase Calculator
Type any date - tonight, a wedding, a camping trip, a historical morning - and this calculator returns the moon's phase name, its emoji, the illuminated fraction and its age in days, plus the next full moon after that date. Everything is computed live in your browser from the 29.5306-day synodic cycle, so the answer arrives before a moon-phase site finishes loading its ads.
Moon almanac sites freeze one year per page and bury the phase behind article text. This one answers any date at once and tells you the size of its own error - about a day - instead of pretending almanac precision. The result lands in your tab title, so the moon follows you while you open other tabs.
How to use
- Pick a date (today is pre-filled).
- Read the phase name, emoji and illuminated percentage.
- Check the next full moon date - or share the result link.
Frequently asked questions
How accurate is this moon phase calculator?
It uses the mean synodic cycle of 29.5306 days counted from a reference new moon, which can drift up to about a day from official almanac times. For minute-precise times an observatory table wins; for any-date answers this is faster than looking one up.
What is the moon phase tonight?
Today's date is pre-filled, so the big emoji shows tonight's phase the moment the page opens, with the illuminated fraction and the next full moon date beside it.
Why does the moon age matter?
Moon age is how many days past new moon the date sits - day 0 is new, about 14.77 is full, and the count explains why full moons shift about 11 days earlier each calendar year.
Does my location change the moon phase?
No - the phase depends only on the date. Where you are changes when the moon rises, not how lit it is.