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Moon Phase Calculator

See the phase of the Moon for any date and time: phase name, how much of the Moon is lit, its age in the lunar cycle, and when the next full moon and new moon happen. A month calendar shows every day's phase, all in your own time zone.

Enter your values to see the result.
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How to use the Moon Phase Calculator

  1. Pick a date, for example today, a birthday or an event.
  2. Set the time if you want the illumination at a particular hour (default 9 PM).
  3. Press Find moon phase to see the phase, illumination, moon age and next full and new moons.
  4. Scroll the moon calendar to see the phase for every day of that month.
  5. Download the calendar as CSV or copy the summary.

How the moon phase is worked out

  • Principal phases (new, first quarter, full, last quarter): computed with the lunar phase series from Jean Meeus, Astronomical Algorithms, chapter 49, using the mean synodic month of 29.530588861 days plus periodic corrections for the Sun's and Moon's orbits.
  • Illumination = (1 + cos i) ÷ 2, where the phase angle i comes from the Moon's elongation from the Sun (Meeus, chapter 48).
  • Moon age = time since the most recent new moon.
  • A day is labeled with a principal phase when the exact moment falls on that local calendar day; other days get the intermediate phase name.

Moon phases at a glance

PhaseApprox. moon ageIlluminationVisible
🌑 New Moon0 days0%Not visible, up with the Sun
🌒 Waxing Crescent1 – 6 days1 – 49%Evening, western sky
🌓 First Quarter7.4 days50%Afternoon to midnight
🌔 Waxing Gibbous8 – 14 days51 – 99%Most of the evening and night
🌕 Full Moon14.8 days100%All night, rises at sunset
🌖 Waning Gibbous16 – 21 days99 – 51%Late evening to morning
🌗 Last Quarter22.1 days50%Midnight to midday
🌘 Waning Crescent23 – 29 days49 – 1%Before dawn, eastern sky

Ages are averages; the exact time between phases varies by up to about a day because the Moon's orbit is elliptical.

Frequently asked questions

What are the phases of the Moon?

There are four principal phases: new moon, first quarter, full moon and last (third) quarter. Between them are the intermediate phases: waxing crescent, waxing gibbous, waning gibbous and waning crescent. Waxing means the lit part is growing; waning means it is shrinking.

How long is a lunar cycle?

The synodic month, from one new moon to the next, averages 29.53 days (29 days, 12 hours, 44 minutes). Individual cycles vary from about 29.27 to 29.83 days because the Moon's orbit is elliptical.

How is the moon phase calculated?

The exact times of new, quarter and full moons come from the astronomical algorithm in Jean Meeus' Astronomical Algorithms, accurate to about a minute. Illumination is calculated from the Moon's phase angle as (1 + cos i) ÷ 2, using its position relative to the Sun.

What does moon age mean?

Moon age is the number of days since the last new moon. About 0 to 1 days is a new moon, around 7.4 days is first quarter, around 14.8 days is full moon and around 22.1 days is last quarter.

Why is the full moon on a different date in some countries?

A full moon happens at one instant worldwide, but the local date depends on the time zone. A full moon at 02:00 UTC on the 15th is still the evening of the 14th in the Americas. This calculator shows times in your device's time zone.

Does the Moon look the same everywhere on Earth?

The phase and illumination are the same everywhere at a given moment, but the Moon appears flipped in the Southern Hemisphere compared with the Northern, so a waxing crescent is lit on the right in the north and on the left in the south.

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