Moon Phase Calculator

Our Moon Phase Calculator provides you with the current moon phase, its illumination percentage, and the exact date of the next full moon. Understanding moon phases can be useful for planning outdoor activities, gardening, or simply satisfying your curiosity about our celestial neighbor. For instance, knowing the moon's illumination is crucial for stargazing, and in 2026, the first full moon will occur on January 13th.

This calculator uses an astronomical algorithm to determine the moon's phase and illumination. It calculates the Julian date from the current date and time, then uses a series of orbital parameters and trigonometric functions to determine the moon's position relative to the Earth and Sun. The illumination percentage is derived from the angular separation between the moon and the sun as viewed from Earth, while the next full moon date is found by iterating forward from the current time until a full moon (0 or 360 degrees phase angle) is detected.

While the calculator provides highly accurate data, remember that moon phase observations can be affected by local weather conditions like cloud cover. Also, be aware that the 'next full moon' date displayed is based on Universal Time (UT) and may need adjustment for your specific time zone. A common mistake is to confuse the new moon with a completely dark sky; even during a new moon, some faint illumination or earthshine might be visible under ideal conditions.