Moon Sign Calculator
Find where the Moon stood at the minute you were born: your Western and Vedic Moon signs, the exact degree, and the phase you arrived under.
The Moon changes sign every two to three days, and on about four birthdays in ten it does so during the day. No time? We check the whole day and tell you whether it matters.
Your Moon sign is the zodiac sign the Moon was passing through when you were born. If your Sun sign describes how you set out to shine, your Moon sign describes what happens underneath: how you react before you think, what makes you feel safe, and what you need from the people close to you. Many astrologers consider it the most personal placement in the chart.
Why your birth time matters
The Sun spends about a month in each sign; the Moon spends only two and a half days. On roughly four birthdays in ten, the Moon moves into a new sign at some point during the day, so a calculator that only asks for your date is guessing on those days. This one uses the exact minute and place of your birth. If you don’t know the time, it checks the whole day and tells you plainly whether the answer depends on it.
Western or Vedic: why two answers?
Western astrology uses the tropical zodiac, which is tied to the seasons: 0° Aries is the March equinox. Vedic astrology uses the sidereal zodiac, which is tied to the stars. Because the equinox slowly drifts against the stars, the two zodiacs are now about 24° apart, so your Vedic Moon is often one sign behind your Western Moon. Neither is a mistake; they measure from different starting points. We show both, using the Lahiri ayanamsa for the sidereal sign.
How it’s calculated
Your local birth time is converted to Universal Time using your birthplace’s historical time zone, daylight saving included. The Moon’s apparent position is then computed with the open-source Astronomy Engine, which we checked against NASA JPL Horizons: it agrees within a few arc-seconds. The Moon phase comes from the angle between the Moon and the Sun (0° at new moon, 180° at full), and the percentage lit follows from that angle.
Frequently asked
What is a Moon sign?
It is the zodiac sign the Moon occupied at the moment you were born. In astrology the Moon represents your emotional nature: your instincts, moods, comforts and the way you look after yourself and others. It is often read alongside the Sun sign and the rising sign as the core of a birth chart.
Do I need my birth time to find my Moon sign?
It helps a lot. The Moon changes sign every two to three days, and on about four days in ten the change happens during that calendar day. With your birth time and place we compute the Moon for the exact minute. Without a time we scan the whole day: if the sign doesn’t change, the answer is certain, and if it does, we show both options with the time of the switch.
Why is my Vedic Moon sign different from my Western one?
Western astrology measures signs from the March equinox (tropical zodiac); Vedic astrology measures them from the fixed stars (sidereal zodiac). The gap between the two, called the ayanamsa, is about 24° today, so the Vedic Moon often lands one sign earlier. We use the Lahiri ayanamsa, the standard in Indian astrology.
What does the Moon phase at birth mean?
The phase shows the relationship between the Sun and the Moon when you were born. Astrologers such as Dane Rudhyar linked each phase to a temperament, from the instinctive new-moon type to the aware, relationship-minded full-moon type. We give the phase name, the percentage of the Moon that was lit, and its angle from the Sun.
How accurate is this calculator?
The astronomy is not the weak point. Our Moon positions agree with NASA JPL Horizons within a few arc-seconds. The real uncertainty is the birth time: the Moon moves about half a degree an hour, so a time that is off by 30 minutes shifts it by roughly a quarter of a degree. If you are close to a sign border, the calculator tells you how many minutes of error would change the answer.
Is it free, and what happens to my data?
It is free and needs no sign-up. The only thing sent to our server is the place name, so we can look up its coordinates and time zone. The astronomy runs in your browser, and your date and time are not stored.
Your Moon is one voice in the chart
Your Moon sign is only the beginning. Arcana Origin reads your full birth chart, Western and Vedic, alongside dozens of other traditions from the same birth moment.
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