Moon Phase Calculator
Calculate the moon phase for any date.
Get the lunar phase name, illumination percentage, moon age in days, and days until the next new or full moon.
Moon phase calculation determines the current phase of the moon based on the number of days elapsed since the last new moon. The lunar cycle repeats every 29.53059 days — called the synodic month.
Current moon age formula: Moon Age (days) = Days since known New Moon (mod 29.53059)
Phase determination from age:
- 0–1.85 days: 🌑 New Moon
- 1.85–7.38 days: 🌒 Waxing Crescent
- 7.38–9.22 days: 🌓 First Quarter
- 9.22–14.77 days: 🌔 Waxing Gibbous
- 14.77–16.61 days: 🌕 Full Moon
- 16.61–22.15 days: 🌖 Waning Gibbous
- 22.15–23.99 days: 🌗 Last Quarter
- 23.99–29.53 days: 🌘 Waning Crescent
Moon illumination percentage: Illumination % = (1 − cos(Moon Age × 360° ÷ 29.53)) ÷ 2 × 100
Traditional gardening guide by moon phase:
- New Moon to First Quarter (Waxing Crescent): Plant leafy crops and annuals (lettuce, spinach, cabbage), rising sap, good germination
- First Quarter to Full Moon (Waxing Gibbous): Plant fruiting crops (tomatoes, squash, peppers, beans), increased moisture in soil
- Full Moon to Last Quarter (Waning Gibbous): Plant root vegetables, bulbs, and perennials (carrots, beets, garlic, trees)
- Last Quarter to New Moon (Waning Crescent): Rest, weed, harvest, till, apply compost, minimal planting
What each variable means:
- Synodic month (29.53 days): measured from new moon to new moon; different from the sidereal month (27.32 days), which measures the moon’s orbit relative to distant stars
- Gravitational effect on water: the same tidal forces that pull ocean water also affect soil moisture; this is the theoretical basis for biodynamic and lunar gardening
- Lunar perigee: when the moon is closest to Earth (largest apparent size); associated with stronger tidal forces and what is popularly called a “supermoon”
Worked example: A known New Moon occurred on January 11, 2024. What phase was the moon on February 5, 2024?
Days elapsed = January 11 to February 5 = 25 days Moon age = 25 mod 29.53 = 25 days (under one full cycle) Phase = 23.99–29.53 days → Waning Crescent
Illumination = (1 − cos(25 × 360° ÷ 29.53)) ÷ 2 × 100 = (1 − cos(305.4°)) ÷ 2 × 100 = (1 − 0.571) ÷ 2 × 100 = 21.5% illuminated
Gardening action for this phase: focus on weeding, harvesting root vegetables, and preparing beds for the upcoming new moon planting cycle.