Moon Phase Calculator (Moon Phase Today and on Any Date)

The Moon goes from new to full and back in about 29.5 days. This calculator shows its phase for any date, time and time zone: the phase name, how much of the disk is lit and the Moon's age in days, plus when the next new, first quarter, full and last quarter moons occur. A calendar table shows every day of the month, handy for planning night photography, fishing or stargazing.

How to use this tool

1. Pick a date and a local time (the default 21:00 is a typical viewing time).
2. Choose your time zone so phase times are shown in your clock time.
3. Choose northern or southern hemisphere to orient the moon icons.
4. Read the phase and illumination, and the table for the whole month.

Formula

JDE = 2451550.09766 + 29.530588861k + … (Meeus ch. 49) · illuminated fraction k = (1 + cos i) ÷ 2

k counts lunations from the new moon of 6 January 2000; quarter values (k + 0.25, + 0.5, + 0.75) give the other phases. Periodic terms for the Sun's and Moon's anomalies, the Moon's latitude argument and 14 planetary terms bring each instant to within about a minute. The phase angle i comes from the Moon's elongation (Meeus 48.4). The Moon's age is the time since the last new moon.

Example

From 1 January 2026, 12:00 UTC, the next full moon is 3 January at about 10:03 UTC (1.92 days later) and the next new moon 18 January at about 19:52 UTC, matching the US Naval Observatory. On 26 January 2026 at 04:47 UTC the Moon is exactly at first quarter, half lit.