Moon Sign Calculator

Your Moon sign is the zodiac sign the Moon occupied at the moment you were born. Where the Sun sign describes what you are consciously building over a lifetime, the Moon is read as the private self underneath it: your emotional reflexes, what you need in order to feel safe, how you react before you have had time to think, and what you do when you are hurt. It is the placement people recognise in themselves most immediately, and the one that most often explains why two people with the same star sign are nothing alike.

It is also the placement most often got wrong, because the Moon moves fast. The Sun covers about one degree a day; the Moon covers thirteen, which is a whole zodiac sign every two and a half days. That means the Moon changes sign at some point during roughly two days in every five, and on those days a birth date alone genuinely cannot tell you which side of the line you fall. A calculator that quietly assumes noon will be confidently wrong for anyone born on the far side of the change.

This tool handles that case properly. Give it a birth time and it computes the Moon's position for that exact instant, converting your local time using the time-zone rules actually in force on the day. Leave the time out and it brackets the whole day, computes the Moon at both ends, and tells you either that your sign is settled or that it is genuinely one of two. The Moon's position comes from the full sixty-term lunar series in Meeus's Astronomical Algorithms and agrees with JPL Horizons, NASA's ephemeris service, to within six arcseconds. Everything runs in your browser and nothing you enter is uploaded or stored.