Moon phase calculator
Find the moon's phase, illumination and age for any date, plus the nearest new and full moons.
Moon phase calculator
Type a date and this tool works out what the moon looked like — or will look like — that night: which of the eight named phases it was in, how much of the disc was lit, and how many days had passed since the previous new moon. Leave the field empty and it uses today's date automatically, so the page is useful the moment it loads. Anyone tracking a lunar calendar, planning stargazing or a night photo shoot, or just curious what phase the moon was in on a birthday or anniversary can paste a date and get an instant answer.
Dates can be typed as ISO (2026-08-31) or the common dotted European format (31.08.2026). The result always includes an emoji for the phase — 🌑🌒🌓🌔🌕🌖🌗🌘 — so the shape is visible at a glance, not just named. Turn on "Show next new/full moon dates" to see how many days remain until the next occurrence of each, and "Show full month calendar" to list every day of that month with its own phase and illumination percentage in one block, handy for planning around a specific lunar event.
The calculation is a local astronomical approximation: it measures days elapsed since a known reference new moon and divides that by the average synodic month (29.53 days) to get age, illumination and phase. That is accurate to within roughly a day for any date — plenty for planning purposes — without needing a full ephemeris or any external data source. Invalid or unrecognized dates produce a clear message instead of a wrong answer.
Everything runs locally in your browser using ordinary JavaScript math — no date you type is ever sent anywhere. Copy the result, download it as a .txt file, or send it straight to another tool's input to keep working.