Also available in: Português (Brasil)
Moon phase today
The eight phases of the Moon
| Phase | Typical illumination | How it looks in the sky |
|---|---|---|
| New moon | 0% | Rises and sets with the Sun; dark night, good for stargazing |
| Waxing crescent | about 25% | Thin sliver in the west just after sunset |
| First quarter | 50% | Half lit; high in the sky at dusk |
| Waxing gibbous | about 75% | Almost full, only a slice missing |
| Full moon | 100% | Rises at sunset and lights the whole night |
| Waning gibbous | about 75% | Shrinking from the opposite edge, rises after dusk |
| Last quarter | 50% | Half lit; high in the sky at dawn |
| Waning crescent | about 25% | Sliver in the east before sunrise |
The Moon in Brazilian culture
In Brazil the phase of the Moon guides haircuts, planting and fishing. We record it as declared tradition, not as advice: the only proven physical effect of the Moon on daily life is the tides.
| Phase | Custom | Status |
|---|---|---|
| Waxing | Cut hair so it grows back stronger | Folk tradition, no scientific basis |
| Full | Fishing and sowing leafy crops | Rural lore; spring tides are real, the rest is folklore |
| Waning | Cut hair to slow regrowth; prune | Folk tradition, no scientific basis |
| New | Let the soil rest and replan | Folk tradition, no scientific basis |
How the moon phase is calculated
The moon phase is the angle between the Sun and the Moon as seen from Earth. When that angle is zero the Moon is new, invisible beside the Sun; at 90 degrees we see the first quarter, half lit; at 180 degrees the full moon, opposite the Sun; at 270 degrees the last quarter. This page computes that angle at the moment you open the site, right in your browser, with the astronomy-engine, an open source MIT licensed library that resolves the Moon's position to better than a tenth of a degree. From it come the phase among the eight, the illuminated percentage, the age of the Moon in days since the last new moon, and the exact dates of the next new moon and the next full moon.
The full cycle of phases, the synodic month, averages 29.53 days, a little longer than the Moon's orbit around Earth (27.32 days), because while the Moon orbits, Earth also moves around the Sun and the Moon needs two extra days to realign. The tides follow this rhythm: at new and full moon the Sun and Moon pull in line and tides run strongest, the spring tides; at the quarters, with Sun and Moon at a right angle, tides run weakest, the neap tides. That is gravitational physics, verifiable every month at any harbour.
Transparency: the phase, the illumination and the dates are computed astronomy, checked against public ephemerides. The traditions of cutting hair, planting or fishing by the phase of the Moon are declared folk culture, with no scientific evidence of any effect on the body or on crops, and nothing here is health or farming advice. Privacy: the whole calculation runs on this page and nothing leaves your browser.
Last updated: · Methodology and sources