Moon Phase Calculator
Select any date to see the Moon’s age, illumination percentage, and phase description using a simplified astronomical model.
Date: Tuesday, November 25, 2025
Moon age
4.45 day(s)
0 = new moon • 14.765294335 ≈ full moon
Illumination
20.8%
Waning Gibbous
Brightness decreases after full moon, shrinking from the right.
How to Use This Calculator
Select a calendar date
Choose the day you want to examine—past, present, or future.
Understand the phase
Review the lunar age, illumination percentage, and descriptive phase name.
Plan ahead
Use upcoming new/full moon predictions to schedule stargazing, rituals, or photography.
Formula
Days Since New = Selected Date − 2000-01-06 18:14 UTC
Moon Age = Days Since New mod 29.53058867
Illumination = (1 − cos(2π × Age / Synodic Month)) ÷ 2
Example: Age 14.77 days → illumination ≈ 99% → near full moon.
Why Moon Phases Matter
Lunar phases influence tides, cultural events, and night-sky brightness. Photographers, gardeners, and astronomers plan around the Moon’s cycle.
- Plan astrophotography sessions for dark (new moon) nights.
- Schedule fishing or hunting trips according to moonrise illumination.
- Track lunar-inspired rituals, meditation, or journaling practices.
- Align planting schedules with waxing/waning phases in lunar gardening traditions.
Frequently Asked Questions
How accurate is this calculator?
It’s typically within a few hours of published values. For second-level accuracy, reference NASA/JPL data.
Does location matter?
The phase and illumination are global. For rise/set times, you need your latitude/longitude.
Why use 2000-01-06 as a base?
It’s a widely used reference new moon from astronomical tables, making calculations consistent.
Can I get moonrise/moonset times?
This tool focuses on phase. For rise/set, consult an astronomy almanac or planetarium app.