Guides
What is the moon phase today?
The reading below is computed the moment you open the page — same algorithms, same wording as the Plenilune app.
How to read tonight's moon
Two numbers describe the Moon on any given night. The phase names the geometry — where the Moon stands in its 29.53-day cycle from new to full and back. The illuminated fraction says how much of the visible disc is lit, from 0% at new moon to 100% at full. Between the two, the direction matters: a waxing moon grows toward full, a waning moon shrinks toward new.
A quick trick for the northern hemisphere: when the lit side is on the right, the Moon is waxing; on the left, it is waning. In the southern hemisphere the trick is exactly reversed — see our guide on why the Moon looks upside down south of the equator.
Why apps can disagree by a percent or a day
The illuminated fraction changes continuously — up to a percent in a few hours near the quarters — so two apps consulted at different moments will honestly differ. Phase names can also differ by a day around the principal phases: the convention Plenilune follows (and this page with it) names new moon, quarters and full moon only on the calendar day when their exact instant falls, in your time zone.
Questions
- Why do two apps show a different illumination percentage?
- Because they compute it at different instants, or round differently. The fraction moves continuously — the honest answer is a number that keeps changing through the night. Differences of one or two percent are normal; differences of ten mean one of the apps is wrong.
- What does waxing and waning mean?
- Waxing means the lit fraction is growing, from new moon toward full; waning means it is shrinking, from full back to new. Each half of the cycle lasts about two weeks.
- Can I see the moon phase for a past or future date?
- Yes — the Moon's motion is fully predictable. In the Plenilune app the calendar walks decades in both directions, offline, with the same algorithms as this page.