Power Calculators

🌙 Moon Phase Calculator

Calculate the Moon age, phase position, approximate illumination and eight-phase lunar phase code for any date.

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Enter details

Choose the date for which you want to estimate the Moon phase.

Fill in the details and click Calculate to see your results.


Also available in our Android app, with charts and full breakdown tables.

📘 About the Moon Phase

The Moon goes through a repeating sequence of phases as its illuminated portion changes from Earths viewpoint.

The average interval from one new moon to the next is approximately 29.530588853 days.

This calculator uses January 6, 2000 at 18:14 UTC as a reference new moon.

The result is a mean-cycle approximation and is not intended to replace a precise astronomical ephemeris.

✏️ Worked examples

Example 1 - Reference new moon

You enter
Date6 Jan 2000
You get
Moon Age (days)4.2375
Lunar Cycle Fraction0.143495
Approximate Phase Angle (degrees)51.6583
Phase Code (0-7)1
Approximate Days to Next New Moon25.2931
Approximate Days Relative to Full Moon10.5278

January 6, 2000 at the reference epoch corresponds to the beginning of the modeled lunar cycle.

Try this example →

Example 2 - Full moon position

You enter
Date19 Dec 2021
You get
Moon Age (days)19.4479
Lunar Cycle Fraction0.658569
Approximate Phase Angle (degrees)237.085
Phase Code (0-7)5
Approximate Days to Next New Moon-19.4479
Approximate Days Relative to Full Moon-4.68263

A date approximately half a synodic month after a new moon is near the full-moon portion of the cycle.

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Example 3 - Current-date calculation

You enter
Date1 Oct 2026
You get
Moon Age (days)24.1432
Lunar Cycle Fraction0.817565
Approximate Phase Angle (degrees)294.323
Phase Code (0-7)7
Approximate Days to Next New Moon-24.1432
Approximate Days Relative to Full Moon-9.37788

Choose any date to calculate its position in the mean lunar cycle.

Try this example →

🧭 How to use this calculator

What you enter

  • DateChoose the date for which you want to estimate the Moon phase.

What you get

  • Moon Age (days)
  • Lunar Cycle Fraction
  • Approximate Phase Angle (degrees)
  • Phase Code (0-7)
  • Approximate Days to Next New Moon
  • Approximate Days Relative to Full Moon

💡 Eight Moon phases

  • Phase code 0 = New Moon.
  • Phase code 1 = Waxing Crescent.
  • Phase code 2 = First Quarter.
  • Phase code 3 = Waxing Gibbous.
  • Phase code 4 = Full Moon.
  • Phase code 5 = Waning Gibbous.
  • Phase code 6 = Last Quarter.
  • Phase code 7 = Waning Crescent.

💡 Mean synodic month

  • The modeled lunar cycle is 29.530588853 days.
  • The cycle is measured from one new moon to the next.
  • The actual timing of lunar phases varies because the Moon does not orbit at a constant angular rate.

💡 Accuracy and limitations

  • This is a mean-cycle calculation rather than a full astronomical ephemeris.
  • The actual new moon and full moon can occur hours away from the mean-cycle estimate.
  • The calculator should not be used for precise eclipse, occultation, navigation or telescope timing.

❓ Frequently asked questions

How long is a lunar cycle?

The mean synodic month is approximately 29.530588853 days.

What are the eight Moon phases?

New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter and Waning Crescent.

What reference does this calculator use?

It uses the known new moon of January 6, 2000 at approximately 18:14 UTC as the reference epoch.

Is this Moon phase calculation exact?

No. It uses the mean synodic cycle and therefore provides an approximation rather than a high-precision ephemeris.

What does waxing mean?

Waxing means the illuminated portion is increasing toward full moon.

What does waning mean?

Waning means the illuminated portion is decreasing after full moon.