Rising Sign Calculator

What is a rising sign?

Your rising sign, or Ascendant, is the zodiac sign that was rising over the eastern horizon at the minute and place you were born. As the Earth turns, all twelve signs rise one after another in the course of a day, so the rising sign changes roughly every two hours.

In a birth chart the Ascendant starts the first house, and with it the whole house system. Astrologers read it as the way you meet the world: your first reactions, the impression you make, how you begin things. Your Sun sign describes your core; the rising sign is the doorway through which people meet it.

Why you need your birth time

Your Sun sign only needs the date, because the Sun spends about a month in each sign. The Ascendant moves about one degree every four minutes, and at northern latitudes some signs rise in under an hour, so a birth time half an hour off can give a different rising sign.

Use the time on your birth certificate or hospital record if you can. That is why the result shows how long before your birth time your rising sign began and how long after it the sign ends, and warns you when you were born within 15 minutes of a change.

If you don’t know your birth time, tick the box: you get your Sun and Moon signs for the day, and both Moon signs if the Moon changed sign that day. Our birth time rectification guide explains how astrologers narrow down an unknown time.

How this calculator works

We show every step, so you can check the result against any other source; “Calculation details” lists the numbers.

Time. Your local birth time is converted to Universal Time (UTC) with the IANA time zone database, including its historical records for each city. If the clocks changed on your birth date, we ask which time you mean, and you can always enter the UTC offset from your birth record.

Ascendant. From Universal Time we compute Greenwich apparent sidereal time and the true obliquity of the ecliptic (Jean Meeus, Astronomical Algorithms, chapters 12 and 22). Adding your longitude gives the local sidereal time (RAMC), and the standard formula gives the Ascendant: ASC = atan2(cos RAMC, −(sin RAMC · cos ε + tan φ · sin ε)), with ε the obliquity and φ your latitude.

Sun and Moon. Their positions come from Astronomy Engine, an open-source astronomy library, in the tropical zodiac used by most Western astrologers.

Checked. On 1,000 births from 1900 to 2050 on every continent, our results matched the Swiss Ephemeris, the reference behind most astrology software, within 0.001° for the Ascendant and the Sun and 0.004° for the Moon, with no case of a different sign.

Sun, Moon and rising sign: what’s the difference?

The Sun sign is the one most people know: the sign the Sun was in on your birthday, shared by everyone born that month. The Moon changes sign every two and a half days and is read as your emotional needs. The rising sign changes every two hours or so and is read as your outward style, the lens through which you meet new situations.

Together they are called the Big Three, and two people with the same Sun sign rarely share all three. Our zodiac sign pages describe each sign, and the birth chart guide shows how the rising sign shapes the rest of the chart.