acalculator

What is the moon phase on my date?

Pick a date, a time and your offset from UTC. The moon phase calculator shows the phase, how much of the Moon is lit and its age in days, and the times of the next new moon, first quarter, full moon and last quarter.

Your numbers

Moon phase
Waning gibbous

Moon phase on October 2, 2026: Waning gibbous, 62.3% lit. Next full moon: 2026-10-26 04:12.

Illuminated
62.3%
Moon age (days)
21.36
Waxing or waning
Waning
Last new moon
2026-09-11 03:27
Next first quarter
2026-10-18 16:13
Next full moon
2026-10-26 04:12
Next last quarter
2026-10-03 13:25
Next new moon
2026-10-10 15:50

Answer for the example date Friday, October 2, 2026. It changes to today's date when the page loads.

Moon phase: Waning gibbous. Moon phase on October 2, 2026: Waning gibbous, 62.3% lit. Next full moon: 2026-10-26 04:12.

How much of the Moon is lit in the days around your date?

How to calculate

Shows the Moon’s phase, illuminated percent and age on any date and time from 1900 to 2149, with the dates and times of the next new moon, first quarter, full moon and last quarter.

Example with the default inputs (Date October 2, 2026, Local time 12:00, UTC offset (hours) 0) on the example date Friday, October 2, 2026: Moon phase on October 2, 2026: Waning gibbous, 62.3% lit. Next full moon: 2026-10-26 04:12.

Method: Phase times: Meeus ch. 49 (mean phase plus periodic and planetary terms), converted from TD to UT with NASA’s ΔT polynomials. Illuminated fraction k = (1 + cos i) ÷ 2 with the phase angle i from Meeus eq. 48.4.

  • Times are to the nearest minute; Meeus gives phase times to within about a minute of the full theory for 1900 to 2100.
  • The phase name is that of a new moon, quarter or full moon that falls on your local date; otherwise crescent (under 50% lit) or gibbous (50% or more), waxing or waning.
  • Illumination is for the Earth’s centre and the time you type.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Date 2026-06-29, Local time 23:56, UTC offset (hours) 0 gives Moon phase Full moon, Last new moon 2026-06-15 02:54, Next last quarter 2026-07-07 19:29, Next new moon 2026-07-14 09:43.Source: Meeus (1998), Astronomical Algorithms, 2nd ed., ch. 49; U.S. Naval Observatory, Phases of the Moon 2026, the check (new moon June 15 02:54, last quarter July 7 19:29, new moon July 14 09:43 UT). https://aa.usno.navy.mil/data/MoonPhases
  2. Date 2026-10-01, Local time 12:00, UTC offset (hours) 0 gives Moon phase Waning gibbous, Waxing or waning Waning, Last new moon 2026-09-11 03:27, Next last quarter 2026-10-03 13:25, Next new moon 2026-10-10 15:50, Next full moon 2026-10-26 04:12.Source: Meeus (1998), Astronomical Algorithms, 2nd ed., ch. 49; U.S. Naval Observatory, Phases of the Moon 2026, the check (new moon Sept 11 03:27, last quarter Oct 3 13:25, new moon Oct 10 15:50, full moon Oct 26 04:12 UT). https://aa.usno.navy.mil/data/MoonPhases
  3. Date 2026-10-10, Local time 09:00, UTC offset (hours) -5 gives Moon phase New moon, Last new moon 2026-09-10 22:27, Next new moon 2026-10-10 10:50, Next full moon 2026-10-25 23:12.Source: Meeus (1998), Astronomical Algorithms, 2nd ed., ch. 49; U.S. Naval Observatory, Phases of the Moon 2026, the check (new moon Sept 11 03:27, new moon Oct 10 15:50, full moon Oct 26 04:12 UT). https://aa.usno.navy.mil/data/MoonPhases

How it works

The instant. Your local date and time minus the UTC offset give a moment in Universal Time (UT), as a Julian Day JD.

Phase times (Meeus chapter 49). For lunation number k (k = 0 at the new moon of 2000 January 6; k + 0.25 is first quarter, + 0.5 full, + 0.75 last quarter) and T = k ÷ 1236.85:

  • Mean phase: JDE = 2451550.09766 + 29.530588861 k + 0.00015437 T² − 0.000000150 T³ + 0.00000000073 T⁴
  • E = 1 − 0.002516 T − 0.0000074 T²; M = 2.5534 + 29.10535670 k − 0.0000014 T² − 0.00000011 T³; M′ = 201.5643 + 385.81693528 k + 0.0107582 T² + 0.00001238 T³ − 0.000000058 T⁴; F = 160.7108 + 390.67050284 k − 0.0016118 T² − 0.00000227 T³ + 0.000000011 T⁴; Ω = 124.7746 − 1.56375588 k + 0.0020672 T² + 0.00000215 T³ (degrees)
  • Add Meeus’s 25 periodic terms for new moon, full moon, or the quarters (with E for terms in M), the quarter correction W (added for first quarter, subtracted for last quarter), and the 14 planetary terms A1 to A14
  • UT = JDE − ΔT ÷ 86,400, with ΔT in seconds from NASA’s polynomial for the decimal year y = year + (month − 0.5) ÷ 12 of the JDE (each polynomial range includes its first year and excludes its last: 1900–1920, 1920–1941, 1941–1961, 1961–1986, 1986–2005, 2005–2050, 2050–2150). Outside 1900 to 2150 (a last new moon in December 1899, or your instant or a next phase in 2150 after the UTC offset is applied) the page extends the nearest polynomial: the 1900–1920 one before 1900, and the 2050–2150 one from 2150 on

Which phases are shown. The last new moon is the latest new moon at or before your instant; the next new moon is the one after it. The next first quarter, full moon and last quarter are the first of each strictly after your instant.

Lit fraction (Meeus chapters 47 and 48) and direction. With T = (JDE − 2451545) ÷ 36525 for your instant: D = 297.8501921 + 445267.1114034 T − 0.0018819 T² + T³/545868 − T⁴/113065000; M = 357.5291092 + 35999.0502909 T − 0.0001536 T² + T³/24490000; M′ = 134.9633964 + 477198.8675055 T + 0.0087414 T² + T³/69699 − T⁴/14712000. Phase angle i = 180 − D − 6.289 sin M′ + 2.100 sin M − 1.274 sin(2D − M′) − 0.658 sin 2D − 0.214 sin 2M′ − 0.110 sin D. Illuminated = (1 + cos i) ÷ 2. The Moon is waxing from the last new moon until the full moon of the same lunation (k + 0.5), and waning from that full moon to the next new moon.

Phase name. If a new moon, first quarter, full moon or last quarter (from the lunations around your instant) falls on your local date, the day takes its name. Otherwise it is "Waxing" or "Waning", then "crescent" below 50% lit or "gibbous" at 50% or more.

Moon age = your instant − the last new moon, in days.

The chart draws the lit percent from 15 days before to 15 days after your instant.

Output format. Phase times are local "YYYY-MM-DD HH:MM" at your UTC offset, rounded to the nearest minute (half a minute rounds up). The lit percent shows 1 decimal and the age 2 decimals, rounded half up. Arithmetic is in 64-bit floats.

Assumptions

  • Dates from 1900-01-01 to 2149-12-31; the UTC offset is −12 to 14 hours, the same for the whole page (a daylight-saving change between your date and a later phase is not applied).
  • The lit fraction is for the Earth’s centre; from one place on Earth it differs by a fraction of a percent.

Worked examples by hand

Meeus example 49.a. The new moon of 1977 February (k = −283) is at JDE 2443192.65118, 1977 February 18 at 3h 37m 42s TD; this page’s algorithm gives the same.

The full moon of 2026 June 29 at 23:56 UT. The day is named Full moon; the last new moon was 2026-06-15 02:54, the next last quarter is 2026-07-07 19:29 and the next new moon 2026-07-14 09:43, the USNO times.

2026 October 1, 12:00 UT. No principal phase falls on that date; the full moon was on September 26, so the Moon is Waning gibbous. Last new moon 2026-09-11 03:27; next last quarter 2026-10-03 13:25; next new moon 2026-10-10 15:50; next full moon 2026-10-26 04:12.

2026 October 10, 09:00 in New York (UTC − 5). The new moon at 15:50 UT is 10:50 local on the same date, so the day is a New moon, though the instant is before it: the last new moon is 2026-09-10 22:27 local (03:27 UT on Sept 11), the next new moon 2026-10-10 10:50, and the next full moon 2026-10-25 23:12 local (04:12 UT on Oct 26).

Other questions people ask

What phase is the moon in today?

The page opens on today’s date at 12:00 UTC. Type your local time and your UTC offset (−5 for New York in winter, −4 in summer) to get the phase where you are.

What are the eight moon phases?

New moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter and waning crescent. New, first quarter, full and last quarter are instants; the page names a day after one of them when it falls on that local date, and uses crescent or gibbous in between.

How is the moon phase calculated?

The page uses Jean Meeus’s Astronomical Algorithms: chapter 49 gives the time of each new moon, quarter and full moon from a mean lunation plus about 40 correction terms, and chapter 48 gives the lit fraction from the Sun-Moon angle. NASA’s ΔT polynomials turn the result into Universal Time.

How accurate are the times?

Within a minute or two of the U.S. Naval Observatory for 1900 to 2100: every 2026 phase on the page matches the USNO table to within 1 minute. Times are rounded to the nearest minute.

How long is a lunar cycle?

A synodic month, from one new moon to the next, averages 29.530588861 days (Meeus), about 29 days 12 hours 44 minutes. Single cycles vary by several hours because the Moon’s orbit is an ellipse.

What was the moon phase on the day I was born?

Type your birth date, the time if you know it, and the UTC offset where you were born. Any date from 1900 to 2149 works. Without a time, the page uses 12:00.