Pick any date and this tool estimates the phase of the moon on that day, from new moon through full moon and back again. It computes the moon age, the number of days since the last new moon, using the average synodic cycle of about 29.53 days measured from a known reference new moon, then maps that age to the familiar phase names and an approximate illumination percentage. That makes it handy for planning stargazing and astrophotography, timing tides and outdoor trips, or simply satisfying curiosity about a birthday or historic date. Keep in mind that this is an approximation based on the mean lunar cycle rather than a full astronomical model, so it can be off by around a day near the exact quarter phases. The date defaults to today and everything is computed locally in your browser.
It computes the moon age from the length of the lunar cycle, which averages about 29.5 days, to place the date within the phase sequence.
It is the fraction of the visible lunar disc that is lit, near zero at a new moon and near 100 percent at a full moon.
Yes. It returns the phase name, illumination and moon age for any date you enter, past or future.
Pick any date and this tool estimates the phase of the moon on that day, from new moon through full moon and back again. It computes the moon age, the number of days since the last new moon, using the average synodic cycle of about 29.
Yes. Moon Phase Calculator is completely free, with no sign-up and no usage limits.
Yes. Moon Phase Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Moon Phase Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.