Moon phase calculator
Show the Moon’s phase, illumination and age for a date, with the next new, quarter and full moons.
A clear answer. Here’s how.
Finds the angle between the Moon’s and the Sun’s ecliptic longitudes (the elongation). The Moon’s longitude uses the 27 largest terms of Meeus’s lunar theory plus the standard additive corrections, and the Sun’s uses the NOAA formulas. Illumination is (1 − cos elongation) ÷ 2, including the Moon’s latitude. New, first quarter, full and last quarter moons are the moments the elongation reaches 0°, 90°, 180° and 270°, found by bisection. Accuracy is within a few minutes for events (eight published new and full moons matched to under 3 minutes) and 1% for illumination.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Date (UTC)
- 2026-03-03
- Time (UTC, HH:MM)
- 11:38
Example result
- Phase
- Full Moon
- Illuminated fraction
- 100.0%
- Moon age (days since new moon)
- 14.0
- Elongation from the Sun
- 180.0°
- Previous new moon
- 2026-02-17 12:03 UTC
- Next new moon
- 2026-03-19 01:25 UTC
- Next first quarter
- 2026-03-25 19:19 UTC
- Next full moon
- 2026-03-03 11:40 UTC
- Next last quarter
- 2026-03-11 09:40 UTC
Phase times are when the Moon’s ecliptic longitude is 0°, 90°, 180° or 270° ahead of the Sun, from the main terms of Meeus’s lunar theory. Event times matched eight published new and full moons to within 3 minutes; illumination is within about 1%. Dynamical time is treated as UT (a difference of about a minute), and the 8 phase names are a conventional simplification. Moonrise and moonset depend on your location and are not shown.