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Moon Phase Calculator

Date & Time

Lunar age, illumination, next full/new moon

Quick Answer

Moon Phase Calculator: Lunar age, illumination, next full/new moon. Moon Phase Calculator uses standard date & time formulas to compute accurate results instantly.

Waxing Gibbous
Moon age 12.4 days · 93.9% illuminated
Moon age12.4 d
Illumination93.9%
Next new moon2026-01-18
Next full moon2026-01-03

Calculation steps

  1. 1Anchor: new moon on 2000-01-06 18:14 UTC; synodic month = 29.53059 days
  2. 2Days since anchor ÷ 29.53059, take fractional part × 29.53059 = moon age 12.42 days
  3. 3Moon age 12.4 d falls in [9.23, 14.77) → Waxing Gibbous
  4. 4Illumination = (1 − cos(2π × age/29.53)) / 2 = 93.9%

Full moons in 2026

2026-01-032026-02-022026-03-032026-04-022026-05-012026-05-312026-06-302026-07-292026-08-282026-09-262026-10-262026-11-242026-12-24

Eight moon phases

PhaseMoon age (days)
New Moon0 – 1.85
Waxing Crescent1.85 – 7.38
First Quarter7.38 – 9.23
Waxing Gibbous9.23 – 14.77
Full Moon14.77 – 16.62
Waning Gibbous16.62 – 22.15
Last Quarter22.15 – 24
Waning Crescent24 – 29.54
The synodic month (new moon to new moon) averages 29.53059 days but varies ±7 hours due to orbital eccentricity — dates here may differ from precise almanacs by up to half a day. Moon phases drive tides: spring tides (largest) occur near new/full moons, neap tides (smallest) near quarters. A "blue moon" is the second full moon in a calendar month (roughly every 2-3 years).

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How to Use

  1. Pick dates or a mode: select start/end dates or switch modes in the Moon Phase Calculator.
  2. Instant calculation: results appear immediately with day/week/month equivalents.
  3. Solve both ways: change any field and everything updates — forward or reverse.
  4. Check the context: read the solar-term/holiday/rule notes on this page.

Key Points

  • Moon Phase Calculator is a free online date & time tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Lunar age, illumination, next full/new moon.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Moon Phase Calculator formula

Moon Phase Calculator uses standard date & time formulas to compute accurate results instantly.

FAQ

How do I use the Moon Phase Calculator?
Open the page and fill in the input fields — results update automatically. Lunar age, illumination, next full/new moon.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on standard calendar arithmetic. Last updated: 2025-07

Authoritative sources:

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

Cite this page: YiJianSuan. Moon Phase Calculator[EB/OL]. https://www.yijiansuan.com/en/c/date/moon-phase

Results provided by this tool are for reference only and do not constitute professional advice.