Skip to content

Moon Sign Calculator

Your Moon sign is the sign of the zodiac the Moon stood in when you were born. The Moon moves through a sign in roughly two to two and a half days, so on some birthdays the time decides; the calculator works it out the way the UmbraLux app does and names the minute of the change.

Date of birth

As exact as you can, ideally from your birth certificate.

Your place is missing? Take the nearest town; a few kilometres hardly change the result.

The calculation runs in your browser. Your birth data is neither sent nor stored; only this device remembers your last entry. · Place data: GeoNames (CC BY 4.0)

How the Moon sign is calculated

The calculator runs the same calculation as the UmbraLux app, in three steps:

  1. 1

    Turn the clock time into Universal Time

    Your birth time is the clock time at your birthplace. With the time zone that applied there on that day (the IANA time zone database knows summer times and older rules), it becomes Universal Time (UTC). Without a time, the calculator takes your whole birthday at your birthplace.

  2. 2

    Calculate the Moon's position

    For that moment the ephemeris gives the Moon's apparent geocentric longitude on the ecliptic of date: where the Moon stood in the zodiac, seen from the centre of the Earth.

  3. 3

    Read the sign

    The longitude divided by 30° gives the sign: 0° to 30° is Aries, 30° to 60° Taurus and so on (tropical zodiac). The remainder is the degree within the sign.

Example: 15 May 1990, 14:30, Berlin

On 15 May 1990 summer time applied in Berlin (UTC+2), so 14:30 was 12:30 Universal Time. At that moment the Moon stood at 27°25′ Capricorn.

It was moving 12.4° a day, about half a degree an hour. The same day, at 19:31, it moved into Aquarius: someone born in Berlin that day without a known time has the Moon in Capricorn or in Aquarius.

What the Moon sign means in astrology

Astrology reads the Moon as your emotional side: what you need to feel safe, how you react before you think, what comforts you. The Sun sign describes your core, the Ascendant how you meet the world; together they are often called the big three of a chart.

In the library

Questions about the Moon sign

Can I calculate my Moon sign without a birth time?

On most birthdays, yes: the Moon changes sign only every two to two and a half days or so. The calculator checks your whole birthday at your birthplace; if the Moon changed sign that day, it names the minute, and you can read your sign from roughly when you were born.

Why does my birthplace matter?

Not for the Moon's position itself, but for your birth moment: the clock time is only meaningful with the time zone and summer time of your birthplace on that day.

Why does another calculator show a different Moon sign?

Mostly because it ignores the birth time or the time zone, or calculates with the Moon's mean position, which can be several degrees off the true one. Vedic astrology uses the sidereal zodiac, whose signs lie about 24 degrees further back at present.

How accurate is the calculator?

It calculates with the ephemeris Astronomy Engine. In 5,000 samples from 1900 to 2100, the Moon's position differed from the Swiss Ephemeris, which many astrology programs use, by 10 arcseconds on average and 71 at most; the Moon covers that in less than three minutes.

Is my data stored?

No. The calculation runs in your browser; your date, time and place are neither sent nor stored. Only your device remembers your last entry, and you can delete it below the form.

Sources

More calculators

All calculators