About the Moon Phase Calculator
This moon phase calculator shows what the moon looks like on any date and time — the phase name, the percentage of the disc that is lit, whether it is waxing or waning and the moon’s age in days since the last new moon. It also gives the exact times of the next new moon and full moon, and a twelve-month table of every new moon, first quarter, full moon and last quarter.
Use it to find the moon phase on your birthday or wedding day, to plan stargazing or astrophotography on a dark new-moon night, to schedule night fishing, hunting or gardening by the moon, or simply to know when the next full moon rises. The illumination chart shows how the moon will change over the following month.
Phase times are computed with Jean Meeus’s astronomical algorithms and are typically accurate to within a couple of minutes. Enter your UTC offset so the dates and times match your local calendar — a full moon just after midnight UTC may fall on the previous evening in the Americas.
How to use the moon phase calculator
- 1Enter the date you are interested in — a birthday, event or tonight.
- 2Set the time and your UTC offset so the result matches your local calendar.
- 3Read the phase, illumination and moon age.
- 4Check the next full and new moon times and the 30-day illumination chart.
- 5Use the 12-month table to plan around future full and new moons.
Formula and method
Phase times use the method in Jean Meeus’s Astronomical Algorithms (chapter 49): the mean time of each new, first-quarter, full and last-quarter moon is found from the lunation number and then corrected with about 40 periodic terms for the eccentric orbits of the Earth and Moon and planetary perturbations. Results are converted from Terrestrial Time to UT and then to your UTC offset.
The illuminated fraction comes from the phase angle i between the Sun and Earth as seen from the Moon (Meeus chapter 48). The moon’s age is the time since the previous new moon. The named phase is a principal phase (New, First Quarter, Full, Last Quarter) when that event falls on your local calendar date, otherwise the crescent or gibbous phase between them.
- k
- Fraction of the moon’s disc that is illuminated (0–1)
- i
- Phase angle: Sun–Moon–Earth angle in degrees
Worked examples
1 October 2026, 9 pm UTC
The September full moon was on 26 September, so on the evening of 1 October the moon is about 20.7 days old and roughly 69% lit, shrinking towards the new moon of 10 October. The next full moon, the Hunter’s Moon, is on 26 October.
Full moon on 26 October 2026
The Hunter’s Moon is full at about 04:12 UTC on 26 October 2026, so at 04:00 the disc is essentially 100% lit. The following new moon comes on 9 November.
New moon in New York, 10 October 2026
The new moon falls at about 15:50 UTC (11:50 AM EDT) on 10 October 2026, so that day is a New Moon in New York and the sky is dark that night. By 8 pm the moon is a few hours past new and already waxing; the next full moon is on 26 October.
Frequently asked questions
What are the eight phases of the moon?+
New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last (Third) Quarter and Waning Crescent. The four “principal” phases are exact instants; the crescent and gibbous phases are the periods between them.
How long is a lunar cycle?+
The average synodic month — new moon to new moon — is 29.53 days. Individual lunations vary between about 29.2 and 29.9 days because the Moon’s orbit is elliptical.
What moon phase was I born under?+
Enter your birth date, and if you know it, your birth time and UTC offset. The calculator shows the phase name, how much of the moon was lit and its age on that day.
What is a Blue Moon?+
In popular use a Blue Moon is the second full moon in a single calendar month, which happens about every 2.7 years. The older definition is the third full moon in a season that has four.
Why is the full moon date different in another country?+
A full moon happens at one instant worldwide. Depending on your time zone that instant can fall on different calendar dates — for example, late evening in the Americas can already be the next day in Europe and Asia.
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