How to Use the Moon Phase Tool
The Moon Phase tool shows tonight's moon at a glance and works entirely offline. Here is everything it does.
Read tonight's phase
Open the page and the disc shows the lit shape of the moon right now, with the phase name and illumination percentage, plus whether it is waxing (growing) or waning (shrinking). None of this needs a location — the phase is the same everywhere on Earth at a given moment.
Plan ahead, and add your location
Below the disc you get the dates of the next full moon and next new moon, and a 30-day calendar so you can pick a dark-sky night or a bright full moon. Want rise and set times? Search a city or use your location and the tool adds moonrise and moonset in that place's local time — the one part that does depend on where you are.
What the illumination percentage tells you
The percentage is the fraction of the moon's visible disc lit by the sun, not how far through the month it is. It reads near 0% at new moon, about 50% at first and last quarter, and 100% at full — so the number alone cannot tell a waxing quarter from a waning one. Pair it with the waxing or waning label to know which half of the roughly 29.5-day cycle you are in.
Using it offline
Because the phase is computed in your browser rather than fetched, the page keeps working with no signal once it has loaded, which is useful on a campsite or a flight. Only moonrise and moonset need a location, and even that calculation runs locally. See how the tool calculates the phase for the formulas behind it.
See tonight's phase, the next full moon and a 30-day calendar.
Open the Moon Phase tool