Moon phase calculator for any date, with a lunar calendar
This moon phase calculator shows the Moon exactly as it looks on any date and time: the phase name, the percentage of the disc that is lit, the Moon’s age in days since the last new moon, its distance from Earth and its apparent size. A list of the next eight principal phases — new moon, first quarter, full moon and last quarter — follows, each with the exact time in your time zone and a countdown, and a month calendar draws a small moon for every day.
Below the calendar, a birthday moon phase finder shows the Moon on the day you — and a partner — were born. Positions come from Jean Meeus’ lunar theory (Astronomical Algorithms, chapter 47), computed in your browser; the full moon of 3 January 2026 lands at 10:04 UTC against the almanac’s 10:03.
How to use the Moon Phase Calculator
- Choose a Date, Time and Time zone, or press Now. Southern-hemisphere viewers can flip the disc so the lit side matches what they see.
- Read the phase name and the illuminated fraction in the panel, then the age, distance and apparent diameter in the tiles.
- Check Next phases for the coming new and full moons and quarters, with exact local times and a “supermoon” badge when a full moon falls near perigee.
- Browse the calendar: each day shows the Moon at local noon and its percentage, with principal phases labelled. Click a day to select it, use the arrows to change month, and download the month as an SVG to print.
Moon Phase Calculator features
Accurate lunar theory
Meeus’ truncated ELP-2000/82 series (60 longitude and 60 latitude terms) gives the Moon’s position to about 10 arcseconds and its distance to about 20 km.
Phase instants
New, quarter and full moments are solved from the Moon–Sun elongation and shown in your zone, daylight saving included.
Illumination, age, distance
The lit fraction from the phase angle, days since new moon, Earth–Moon distance and the apparent diameter with a perigee/apogee note.
True-to-sky icons
The terminator is drawn from the real illuminated fraction, with the lit limb on the correct side for your hemisphere.
Month calendar + SVG
A Monday-first grid of daily moons for any month, exportable as a clean vector file for printing.
Birthday and couple mode
The phase, illumination and cycle day for one or two birth dates, and how far apart in the cycle they fall.
The eight phases and what they mean
The cycle from one new moon to the next — the synodic month — averages 29.53 days but varies by up to about 13 hours, so the calculator searches for each phase instant rather than adding a fixed number of days. For the rising and setting times at your own location use the moonrise and moonset calculator.
| Phase | Elongation from Sun | Lit fraction | When it rises / sets |
|---|---|---|---|
| New moon | 0° | 0% | With the Sun — not visible |
| Waxing crescent | 0–90° | 0–50% | Evening sky after sunset |
| First quarter | 90° | 50% | Rises around noon, sets around midnight |
| Waxing gibbous | 90–180° | 50–100% | Afternoon rise, visible most of the night |
| Full moon | 180° | 100% | Rises at sunset, sets at sunrise |
| Waning gibbous | 180–270° | 100–50% | Rises after dark, high before dawn |
| Last quarter | 270° | 50% | Rises around midnight, sets around noon |
| Waning crescent | 270–360° | 50–0% | Pre-dawn sky before sunrise |
Illumination, age and distance
The illuminated fraction is k = (1 + cos i)/2, where i is the phase angle at the Moon between the Earth and the Sun. The Moon’s age counts from the previous new moon; a “14-day-old” moon is full.
The distance swings between about 356 500 km at the closest perigees and 406 700 km at the farthest apogees, changing the Moon’s apparent diameter from 29.4′ to 33.5′. A full moon within a day of perigee is popularly called a supermoon and appears about 14% wider and 30% brighter than one at apogee. The January 2026 full moon falls at about 357 000 km.
Birthday moon phase for one or two people
The birthday finder works out the phase at your birth moment and the day of the lunar cycle, and draws the Moon as it looked. Add a partner’s birthday to see whether you share a phase (“moon twins”), were born half a cycle apart (a new moon and a full moon, which folklore calls complementary), or somewhere between. The astronomy is exact; the compatibility reading is tradition and entertainment, not prediction or advice. Hindu fasting days follow the tithi rather than the phase — see the Ekadashi, Amavasya and Purnima dates calculator, which places each tithi by sunrise at your location.
Northern and southern views
Phase is the same for everyone on Earth at a given instant, but the orientation is not. From the northern hemisphere a waxing moon is lit on the right; from Australia, South Africa or Brazil the same moon is lit on the left, and near the equator the terminator runs roughly horizontally. The hemisphere switch mirrors the icons. The star chart plots the Moon among the constellations, and the eclipse countdown lists eclipse-making new and full moons.
Moon Phase Calculator FAQ
What is the moon phase today?
Press Now. The panel shows the phase name and illumination for the current moment in your time zone; the calendar highlights today.
When is the next full moon?
It is the first “Full moon” row in the Next phases table, with the exact time in your zone and a countdown. The next eight principal phases are listed, covering about two months.
Why does the full moon date differ by a day on some sites?
The instant is the same everywhere, but the calendar date depends on the time zone. A full moon at 22:11 UTC on 1 February 2026 is already 2 February in India and Australia. Set your zone and the calculator uses the right local date.
How accurate is this moon phase calculator?
Phase times are typically within two minutes of almanac values, illumination within a fraction of a percent, distance within about 20 km.
Does the calendar show the Moon as it looks tonight?
Each icon shows the phase at local noon, so the evening Moon is slightly more advanced; use the exact-time view for a specific moment.
What was the moon phase on the day I was born?
Enter your birthday (and birth time if you know it) in the birthday section, with the time zone of your birthplace selected. The Moon moves about 12° a day against the Sun, so a birth time near a phase change can tip the name.