Moon Phase Calculator for Any Date

You're planning a camping trip next weekend and you want to know if there'll be moonlight. Or you're a photographer who wants to shoot under a full moon. Or you're just curious what phase the moon is in right now. Whatever the reason, looking up at the sky only works if the sky is clear and you're outside.

Pick a date, see the moon

The moon phase calculator shows you the current moon phase with an SVG visualization — the lit and shadowed portions of the lunar disc, matching what you'd see from the northern hemisphere. Below the visual, you see the phase name (waxing crescent, first quarter, waning gibbous, etc.), the illumination percentage, and the moon's age in days since the last new moon.

Navigate forward or backward by day, or jump to any date using the date picker. There's also a 14-day strip below showing the upcoming phases as small thumbnails, so you can quickly find the next full moon or new moon without clicking through one day at a time.

The 29.53-day cycle

The moon goes through its complete cycle of phases every 29.53 days (the synodic month). New moon → waxing crescent → first quarter → waxing gibbous → full moon → waning gibbous → last quarter → waning crescent → new moon again. The calculator shows all eight named phases and places your selected date within the cycle.

The illumination percentage is useful for practical planning. At first quarter (day ~7), the moon is 50% illuminated but it sets around midnight — good for early evening light. A waning gibbous (day ~18-21) rises late and is around 60-80% lit — useful if you're out past midnight.

For the moon phase calculator, the underlying algorithm uses known new moon reference dates and the synodic period to calculate the moon's age for any date. It's accurate enough for general planning, photography, and education. If you want to explore the planets as well, the planet comparator shows data for all eight planets.