Quick answer
Decans in astrology are the three 10 degree sections of each 30 degree zodiac sign. A planet in the first decan (0 to 9 degrees) is read as the purest form of the sign, while the second (10 to 19) and third (20 to 29) decans take on a flavor from a sub-ruler. Which sub-ruler depends on the system: the modern triplicity method or the older Chaldean order.
Key takeaways
- Each zodiac sign is 30 degrees wide and splits into three decans of 10 degrees each.
- In the modern triplicity system, the second and third decans borrow flavor from the other two signs of the same element.
- The older Chaldean system assigns decan rulers in a fixed planetary order and gives different answers, so always say which system you mean.
- Decans add nuance to a sign reading; they do not replace the sign, and the rest of the chart usually explains more of the difference between two people.
Decans are the three 10 degree slices inside each 30 degree zodiac sign. A planet at 4 degrees Leo and a planet at 26 degrees Leo are both in Leo, but they sit in different decans, and astrologers read the second one with a slightly different flavor.
If you have ever met two people with the same Sun sign who seem nothing alike, decans are one of the first explanations astrology offers. They are not the biggest one. The Moon, the rising sign, Venus and the rest of the chart usually explain far more. But decans are simple, they only need a degree, and they give a sign reading some welcome texture. This guide explains how to find yours, the two systems astrologers use (which give different answers), and what decans add in love and at work.
What are decans in astrology?
A decan is one third of a zodiac sign: 10 degrees of the sign's 30. The first decan runs from 0 to 9 degrees 59 minutes, the second from 10 to 19 degrees 59 minutes, and the third from 20 to 29 degrees 59 minutes. Every sign has three, so the zodiac has 36 decans in total.
Some background. The zodiac is a 360 degree circle split into twelve 30 degree signs. Each planet in your chart sits at a specific degree of a specific sign, for example Venus at 17 degrees Libra. The degree is what places a planet in a decan. Each decan is given a sub-ruler, a planet or sign that adds a secondary flavor to the main sign.
The idea is old. Chris Brennan traces decans back to ancient Egypt, where 36 star groups marked the hours of the night, and describes how they were later folded into the Greek zodiac. The versions used today are simpler than the Egyptian originals, and there are two of them.
How do you find your decan?
You need the exact degree of the planet you are asking about. For your Sun, that means the day you were born (and, near a sign boundary, the time and place). Then:
- Find the planet's degree within its sign. A chart will show something like "Sun 22 Scorpio 14", meaning 22 degrees and 14 minutes of Scorpio.
- Read off the decan. 0 to 9 is the first decan, 10 to 19 the second, 20 to 29 the third. The Sun at 22 Scorpio is in the third decan.
- Repeat for the planets you care about. Decans apply to every planet, not just the Sun. Your Venus decan and Moon decan are the interesting ones for love.
Because the Sun moves about one degree per day along the zodiac, each Sun decan covers about ten days. Roughly, the first decan is the first ten days after the Sun enters a sign, the second the middle ten and the third the last ten. But the Sun enters each sign on a date that shifts by a day or so from year to year, so a date table is only approximate. If you were born within a day or two of a decan boundary, get the degree from a calculated chart rather than guessing. Being near a sign boundary is a separate issue, covered in born on a cusp.
What are the two decan systems, and why do they disagree?
There are two main ways of assigning sub-rulers, and they give different answers for most decans. Always say which one you are using.
The triplicity system (modern)
This is the version in most modern books and websites. It uses the element groups (the triplicities). The first decan is ruled by the sign's own ruler. The second decan takes its flavor from the next sign of the same element. The third decan takes it from the remaining sign of that element. If elements are new to you, elements and modalities explains them.
Here is the full table.
| Sign | First decan (0 to 9) | Second decan (10 to 19) | Third decan (20 to 29) |
|---|---|---|---|
| Aries | Aries (Mars) | Leo (Sun) | Sagittarius (Jupiter) |
| Taurus | Taurus (Venus) | Virgo (Mercury) | Capricorn (Saturn) |
| Gemini | Gemini (Mercury) | Libra (Venus) | Aquarius (Uranus) |
| Cancer | Cancer (Moon) | Scorpio (Pluto) | Pisces (Neptune) |
| Leo | Leo (Sun) | Sagittarius (Jupiter) | Aries (Mars) |
| Virgo | Virgo (Mercury) | Capricorn (Saturn) | Taurus (Venus) |
| Libra | Libra (Venus) | Aquarius (Uranus) | Gemini (Mercury) |
| Scorpio | Scorpio (Pluto) | Pisces (Neptune) | Cancer (Moon) |
| Sagittarius | Sagittarius (Jupiter) | Aries (Mars) | Leo (Sun) |
| Capricorn | Capricorn (Saturn) | Taurus (Venus) | Virgo (Mercury) |
| Aquarius | Aquarius (Uranus) | Gemini (Mercury) | Libra (Venus) |
| Pisces | Pisces (Neptune) | Cancer (Moon) | Scorpio (Pluto) |
The planets shown are the modern rulers. Astrologers who prefer traditional rulers use Mars for Scorpio, Saturn for Aquarius and Jupiter for Pisces.
The Chaldean system (traditional)
The older method ignores elements. It walks through the seven planets visible to the naked eye in what is called the Chaldean order, from slowest to fastest: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. Starting with Mars at the first decan of Aries, it assigns one planet to each of the 36 decans in turn, repeating the sequence.
That gives Aries the rulers Mars, Sun and Venus; Taurus gets Mercury, Moon and Saturn; Gemini gets Jupiter, Mars and Sun; Cancer gets Venus, Mercury and Moon, and so on round the wheel. The cycle of seven fits into 36 decans five times with one left over, which is why the last decan of Pisces (Mars) and the first decan of Aries (Mars) share a ruler.
Notice the disagreement. In the triplicity system, the second decan of Aries is Leo flavored, ruled by the Sun. In the Chaldean system, it is also the Sun, but that is coincidence: the second decan of Taurus is Virgo and Mercury in one system and the Moon in the other. Traditional astrologers, and the tarot tradition that maps the minor cards to decans, tend to use the Chaldean order. Modern popular astrology almost always uses triplicities.
What does each decan tend to add?
In the triplicity system, the general reading is simple. The first decan is the sign in its most typical form. The second adds a shade of the next sign in its element. The third adds a shade of the last.
A few examples of how that reads:
- First decan Taurus (Taurus flavor): steady, sensual, slow to change. The textbook Taurus.
- Second decan Taurus (Virgo flavor): the same steadiness with more attention to detail, usefulness and getting things right.
- Third decan Taurus (Capricorn flavor): steadiness aimed at ambition and long-term building.
- First decan Libra (Libra flavor): charm, fairness, a strong wish for harmony.
- Second decan Libra (Aquarius flavor): fairness with a cooler, more principled edge and interest in ideas.
- Third decan Libra (Gemini flavor): the same social ease with more talk, more curiosity and a lighter touch.
The pattern is the same for every sign. The decan never overrides the sign; a third decan Libra is still a Libra. It just leans a little.
Do decans change your Venus or Moon sign reading?
They add a shade to it, and that is worth knowing for love. If your Venus is in Cancer, the sign says you love through care, memory and emotional safety. The decan says which kind of Cancer. A first decan Venus in Cancer is the classic nurturer. A second decan (Scorpio flavor) adds intensity and a stronger need for loyalty. A third decan (Pisces flavor) adds softness, imagination and a tendency to idealize.
The same goes for the Moon, which describes what you need to feel safe. A first decan Moon in Aries needs independence. A third decan Moon in Aries (Sagittarius flavor) needs independence and room to explore.
This is one honest answer to "why does my Venus in Cancer friend love so differently from me?" It is not the only answer, and probably not the main one. Aspects to Venus, its house, the Moon sign and the rest of the chart account for more. If you do not yet know your Venus sign, let alone its degree, what is my Venus sign walks through how to find it, and you can find your Venus and Moon free in about 90 seconds. Venara's reports show each planet's sign and degree, so you can read the decan off yourself; the reports do not name decans.
What do decans mean for work?
At work, the decan of your Sun, Mercury or Mars adds a shade to how you operate. A first decan Capricorn Sun is the pure builder. A second decan Capricorn Sun (Taurus flavor) builds with more patience and more attention to comfort and resources. A third decan (Virgo flavor) builds with more analysis and craft.
Mars decans work the same way for how you push. A second decan Mars in Gemini (Libra flavor) argues with more diplomacy than a first decan Mars in Gemini. A third decan Mars in Gemini (Aquarius flavor) pushes for ideas and principles rather than for the win itself.
The strength of reading decans is nuance: it stops "Capricorn" from being one flat description. The pattern to watch is over-reading them. A decan is a 10 degree detail. It should refine a picture that the sign, house and aspects have already drawn, not replace it.
Are decans real, or just a way to make signs more specific?
The 10 degree divisions are real geometry, and the degree of your Sun on your birthday is real astronomy that anyone can check against an ephemeris. The meanings assigned to decans are an interpretive tradition, and one where the two main systems disagree with each other, which is a useful reminder of how much is convention.
March and McEvers include decans in their teaching text as a refinement, not a foundation, and that is a fair weighting. Astrology as a whole is a symbolic language rather than a tested science; controlled studies such as Carlson's 1985 test did not find predictive support. Many people still find sign readings useful for reflection, and decans can make those readings feel a little less generic. That is a reasonable thing to want from them, as long as you remember that a more specific description is not automatically a more accurate one.
What should you do with your decan?
Use it to sharpen the sign readings you already know. Three steps:
- Find the degree of your Sun, Moon and Venus. Write each one as "sign, degree, decan". For example: "Venus, 17 Libra, second decan."
- Read the sign first, then add the decan's flavor. Look up the sub-sign in the table above and ask one question: "Does this shade fit better than the plain sign reading?" Sometimes it does, sometimes not.
- Compare with someone who shares your sign. If you know a person with the same Sun or Venus sign in a different decan, notice where you differ. Then check whether the decan or something else in the chart (the Moon, the rising sign) explains it better. Usually it is something else, and that is worth learning too.
Frequently asked questions
What is my decan?
Your decan depends on the exact degree of a planet in its sign. Degrees 0 to 9 are the first decan, 10 to 19 the second and 20 to 29 the third. For your Sun, the first decan covers roughly the first ten days of the sign, the second the middle ten and the third the last ten. Because the Sun's entry date shifts a little each year, a birth chart with the degree is more reliable than a date table.
What does second decan mean?
A planet in the second decan sits between 10 and 19 degrees of its sign. In the modern triplicity system, the second decan is linked with the next sign of the same element. So a second decan Aries Sun is Aries with a Leo flavor, and a second decan Cancer Moon is Cancer with a Scorpio flavor. The sign still leads; the decan adds a shade.
Are decans the same as cusps?
No. A cusp is the boundary between two signs, and being born near one means the Sun was close to changing sign. A decan is a 10 degree section inside one sign. Someone at 28 degrees Leo is in the third decan of Leo and also near the Leo and Virgo boundary, but they are fully Leo, not part Virgo. Decans describe position within a sign, not blending with the next one.
What is the difference between Chaldean and triplicity decans?
The triplicity system gives each decan a sub-ruler from the same element: the sign's own ruler, then the next sign of that element, then the last. The Chaldean system walks through the seven visible planets in a fixed order (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon) across all 36 decans, starting with Mars at the first decan of Aries. They assign different rulers to most decans, so the same person gets two different sub-rulers.
Do decans matter for compatibility?
A little, and less than the rest of the chart. Two people with Venus in the same sign but different decans may show that sign's love style with slightly different shades. But the Moon, Mars, the 7th house and the aspects between two charts explain far more of a match than decans do. Treat decans as a detail that adds color to a sign reading, not as a compatibility test on their own.
Sources
- Chris Brennan, Hellenistic Astrology: The Study of Fate and Fortune (2017)
- Marion D. March and Joan McEvers, The Only Way to Learn Astrology, Vol. 1
- NASA Science: Sun
About this article
Written and checked by the Venara editorial team against the sources listed and Venara's chart engine. Astrology here is a tool for reflection, not a prediction or professional advice. How we write and check articles.
For entertainment and self-reflection. Not a substitute for professional advice.