Moon Phase Calculator
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Look up the moon phase, how much of the disk is lit, and lunar age in days for any calendar date.
Rates last reviewed: August 2026
Date
Moon phase
Last Quarter
34.3% illuminated · 23.7 days old
- Illumination
- 34.3%
- Lunar age
- 23.7 days
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Moon phases and illumination
The moon cycles through eight commonly named phases about every 29.5 days (one synodic month). Phase names — new moon, first quarter, full moon, and so on — describe how much of the near side is sunlit as seen from Earth, not the moon’s position in the sky.
Illumination is the fraction of the lunar disk that appears lit, from 0% at new moon to roughly 100% at full moon. Lunar age counts days since the last new moon in this simplified model. Real skywatching can differ slightly from tabulated dates because of time zones and the exact instant of each phase.
Example: on August 7, 2026 the moon is typically in a waxing or waning quarter-to-gibbous range depending on the exact date — use the calculator for the phase name, illumination percentage, and age in days for your chosen date.
Official sources
Rates and formulas in this calculator reference the documentation below. Confirm current numbers on the source site before relying on them. Links do not imply endorsement by those organizations of Calcometry or this tool.
Common questions
How accurate is this moon phase estimate?
This tool uses a standard synodic-month formula aligned with almanac-style tables. For official phase times, compare with the U.S. Naval Observatory moon phase data linked below.
Why does my app show a different phase on the same date?
Phase names can flip at local midnight while USNO tables often list the instant of each phase in Universal Time. A few hours near a quarter or full moon can change the label on your calendar date.