Moon Phase Calculator
Discover the moon phase for any date with accurate astronomical calculations
Calculate Moon Phase
Choose any date to see the moon phase
Complete Moon Phase Cycle
Moon Facts
Synodic Month
29.53 days between new moons
Sidereal Month
27.32 days to orbit Earth
Distance
384,400 km from Earth
Diameter
3,474 km (27% of Earth)
Phase Terminology
Waxing
Moon is growing brighter
Waning
Moon is growing dimmer
Gibbous
More than half illuminated
Crescent
Less than half illuminated
Astronomical Tips
Based on precise astronomical algorithms
Uses January 6, 2000 as reference new moon
Accounts for lunar cycle variations
Perfect for astronomy and photography
Understanding Moon Phases
How Moon Phases Work
Moon phases occur due to the changing angles between the Sun, Earth, and Moon as the Moon orbits our planet. The Moon doesn't produce its own light; instead, it reflects sunlight. The portion of the Moon we see illuminated changes as its position relative to the Sun changes.
The Lunar Cycle:
- •Complete cycle takes 29.53 days (synodic month)
- •Eight distinct phases during each cycle
- •Illumination changes from 0% to 100% and back
- •Same phases repeat in a predictable pattern
Calculation Method
Our calculator uses the astronomical algorithm based on a known new moon reference point (January 6, 2000) and the precise synodic month length of 29.53058770576 days.
Reference Point
January 6, 2000, 12:24 PM UTC - Known new moon occurrence
Lunar Day Calculation
Days since reference ÷ 29.53058770576 = Position in lunar cycle
Phase Determination
Lunar day ranges determine specific phase and illumination percentage