Moon Phase Calculator

Find the approximate phase of the Moon for a given date.

Select a date.

-- (Approx. Illumination: --%)

Calculations are based on astronomical algorithms for the Moon's position relative to the Sun and Earth. Results are generally accurate but may differ slightly from highly specialized sources.

Understanding Moon Phases

The Moon doesn't produce its own light; we see it because it reflects sunlight. As the Moon orbits the Earth, the angle between the Sun, Earth, and Moon changes, causing the illuminated portion we see from Earth to vary. This cycle of changing appearance is known as the phases of the Moon.

The Main Moon Phases

  • New Moon:** The Moon is between the Earth and Sun; the sunlit side faces away from Earth. Appears dark.
  • Waxing Crescent:** A small sliver of the Moon becomes visible as it moves away from the Sun in the sky. Waxing means growing.
  • First Quarter:** The Moon has completed about a quarter of its orbit; we see half of the Moon illuminated (the right half in the Northern Hemisphere).
  • Waxing Gibbous:** More than half the Moon is illuminated, and the lit portion continues to grow.
  • Full Moon:** The Earth is between the Sun and Moon; the entire face of the Moon visible from Earth is illuminated.
  • Waning Gibbous:** After the Full Moon, the illuminated portion starts to decrease. Waning means shrinking.
  • Third Quarter (or Last Quarter):** We see the other half of the Moon illuminated (the left half in the Northern Hemisphere).
  • Waning Crescent:** A small sliver remains visible before the cycle returns to New Moon.

How to Use

  1. Select the Date for which you want to know the Moon phase.
  2. Click "Calculate Moon Phase".

The calculator uses astronomical algorithms to determine the Moon's phase and approximate illumination percentage for the selected date.

Knowing the Moon phase can be useful for gardening, fishing, photography, astronomy, or simply appreciating the natural cycles.