AstraLinkGlossary
Decans in astrology: the three faces of every sign and how to find yours
Ever met two Scorpios who had nothing in common? Decans are the reason. Every sign is cut into three ten-degree slices, each with a planetary sub-ruler that tilts the sign's traits. This page explains what decans are, where they came from, how to find yours from your birthday or your chart, what each of the 36 means, and why they are the secret to compatibility inside a single sign.
Decans in astrology are the three 10-degree divisions of each 30-degree zodiac sign, making 36 decans in all. Each decan has a sub-ruler that modifies the sign's core traits, which is why people born early, middle or late in the same sign can feel noticeably different. The system dates back to ancient Egyptian star calendars.
What is a decan in astrology?
A decan (also decanate) is one third of a zodiac sign: the first 10°, the second 10° or the last 10° of its 30°. Twelve signs times three gives 36 decans, each about ten days long in the calendar. The word comes from Greek dekanos, "ruler of ten", and the idea is older than the zodiac itself. Ancient Egyptians tracked the night by the rising of 36 star groups, one every ten days, and used them as a clock and a calendar as early as the third millennium BCE. Hellenistic astrologers in Egypt folded those 36 "faces" into the twelve signs, and the decans have been part of Western astrology ever since; they also survive in tarot, where the 36 numbered minor arcana cards from two to ten each correspond to one decan.
What a decan does is refine the sign. Every decan keeps its sign's element, modality and main ruler, but adds a sub-ruler that colours it. The first decan of any sign is the purest expression of that sign; the second and third blend in a related planet. That is why a Scorpio born on 24 October reads as classic Scorpio, while one born on 18 November can seem softer and more Cancerian: same sign, different decan.
Two systems assign the sub-rulers. The triplicity method, used by most modern astrologers and on this site, gives each decan to the three signs of the same element in zodiac order: Aries's decans are ruled by Aries (Mars), Leo (Sun) and Sagittarius (Jupiter). The older Chaldean method runs the seven classical planets in descending order of speed, starting from Mars at 0° Aries, so the same three Aries decans belong to Mars, the Sun and Venus. The first decan comes out the same in both; the second and third differ, and traditional astrologers still use the Chaldean faces as a minor dignity.
How to find your decan
By birthday. Each decan covers about ten days. The first decan starts on the day the Sun enters the sign, the second about ten days later, the third about twenty days later. The full table below this article has every date range. Because the Sun enters signs on slightly different days each year, anyone born within a day of a decan boundary should use the degree method.
By degree. Open your birth chart and read the degree of your Sun: 0° to 9°59' is the first decan, 10° to 19°59' the second, 20° to 29°59' the third. The same rule applies to every other placement, so you have a Moon decan, a Venus decan and a rising decan too. The AI reading in the app notes the decan where it changes the interpretation, and the Academy covers decans in its signs module.
Virgo decans, as the most-searched example: the first decan (about 23 August to 2 September, 0° to 10°) is Virgo ruled by Mercury, the analyst, precise and verbal; the second (about 3 to 12 September, 10° to 20°) is sub-ruled by Capricorn and Saturn, the builder, disciplined and ambitious; the third (about 13 to 22 September, 20° to 30°) is sub-ruled by Taurus and Venus, the artisan, sensual and patient. Someone born on 14 September is a third-decan Virgo, which is why the birthday profile reads warmer than the stereotype. And a Virgo born on 22 September sits on the Virgo-Libra cusp, which is really just the last degrees of the third decan.
The decans of every sign (triplicity method)
Sub-rulers listed as sign / planet; the first decan always belongs to the sign itself.
- Aries: I Aries / Mars (the pioneer); II Leo / Sun (the performer); III Sagittarius / Jupiter (the explorer).
- Taurus: I Taurus / Venus (the sensualist); II Virgo / Mercury (the craftsperson); III Capricorn / Saturn (the builder).
- Gemini: I Gemini / Mercury (the messenger); II Libra / Venus (the diplomat); III Aquarius / Uranus (the inventor).
- Cancer: I Cancer / Moon (the nurturer); II Scorpio / Pluto (the guardian); III Pisces / Neptune (the dreamer).
- Leo: I Leo / Sun (the sovereign); II Sagittarius / Jupiter (the adventurer); III Aries / Mars (the champion).
- Virgo: I Virgo / Mercury (the analyst); II Capricorn / Saturn (the builder); III Taurus / Venus (the artisan).
- Libra: I Libra / Venus (the partner); II Aquarius / Uranus (the reformer); III Gemini / Mercury (the negotiator).
- Scorpio: I Scorpio / Pluto (the intense one); II Pisces / Neptune (the mystic); III Cancer / Moon (the protector).
- Sagittarius: I Sagittarius / Jupiter (the philosopher); II Aries / Mars (the crusader); III Leo / Sun (the showman).
- Capricorn: I Capricorn / Saturn (the executive); II Taurus / Venus (the steward); III Virgo / Mercury (the strategist).
- Aquarius: I Aquarius / Uranus (the original); II Gemini / Mercury (the communicator); III Libra / Venus (the idealist).
- Pisces: I Pisces / Neptune (the visionary); II Cancer / Moon (the empath); III Scorpio / Pluto (the transformer).
Because modalities do not change within a sign, all three Scorpio decans are still fixed water; the decan changes the flavour, not the recipe.
Decans in relationships and compatibility
Decans explain most of the exceptions to sign compatibility. Sign-to-sign guides such as the compatibility hub work on the whole 30°, but a third-decan Leo (Aries flavour) and a first-decan Leo (pure Sun) want different things from a partner. Decans also create hidden compatibility: a second-decan Virgo carries a Capricorn undertone, so they often click with Capricorns and Tauruses in a way a first-decan Virgo does not. When someone says "I usually get on with Cancers, but not this one", the answer is nearly always the decan. In synastry, a partner's planets in your Sun's decan (within the same 10°) hit closer than planets elsewhere in the sign, simply because the orbs are tighter. Checking decans is a good first move after Sun signs and before the full chart.
Common misconceptions about decans
- "Decans change your sign." They do not. A third-decan Virgo is a Virgo with a Venus accent, never a Taurus.
- "Decan dates are exact." They shift by a day or so each year. Use the degree of your Sun for anyone near a boundary.
- "There is one correct set of decan rulers." Two well-established systems exist, triplicity and Chaldean. They agree on the first decan and differ on the others.
- "Decans are only for the Sun." Every planet and angle has a decan; the Moon's and the Ascendant's are especially telling.
The Big Three: three layers of you
Sun, Moon and rising sign are where every chart reading starts.
All 36 decans: dates, degrees and sub-rulers
| Sign | Decan I (0°–10°) | Decan II (10°–20°) | Decan III (20°–30°) |
|---|---|---|---|
| Aries | Mar 21 – Mar 30 · Mars | Mar 31 – Apr 9 · Sun (Leo) | Apr 10 – Apr 19 · Jupiter (Sagittarius) |
| Taurus | Apr 20 – Apr 30 · Venus | May 1 – May 10 · Mercury (Virgo) | May 11 – May 20 · Saturn (Capricorn) |
| Gemini | May 21 – May 31 · Mercury | Jun 1 – Jun 10 · Venus (Libra) | Jun 11 – Jun 20 · Uranus (Aquarius) |
| Cancer | Jun 21 – Jul 1 · Moon | Jul 2 – Jul 12 · Pluto (Scorpio) | Jul 13 – Jul 22 · Neptune (Pisces) |
| Leo | Jul 23 – Aug 1 · Sun | Aug 2 – Aug 12 · Jupiter (Sagittarius) | Aug 13 – Aug 22 · Mars (Aries) |
| Virgo | Aug 23 – Sep 2 · Mercury | Sep 3 – Sep 12 · Saturn (Capricorn) | Sep 13 – Sep 22 · Venus (Taurus) |
| Libra | Sep 23 – Oct 2 · Venus | Oct 3 – Oct 12 · Uranus (Aquarius) | Oct 13 – Oct 22 · Mercury (Gemini) |
| Scorpio | Oct 23 – Nov 1 · Pluto | Nov 2 – Nov 11 · Neptune (Pisces) | Nov 12 – Nov 21 · Moon (Cancer) |
| Sagittarius | Nov 22 – Dec 1 · Jupiter | Dec 2 – Dec 11 · Mars (Aries) | Dec 12 – Dec 21 · Sun (Leo) |
| Capricorn | Dec 22 – Dec 31 · Saturn | Jan 1 – Jan 10 · Venus (Taurus) | Jan 11 – Jan 19 · Mercury (Virgo) |
| Aquarius | Jan 20 – Jan 29 · Uranus | Jan 30 – Feb 8 · Mercury (Gemini) | Feb 9 – Feb 18 · Venus (Libra) |
| Pisces | Feb 19 – Feb 29 · Neptune | Mar 1 – Mar 10 · Moon (Cancer) | Mar 11 – Mar 20 · Pluto (Scorpio) |
Dates are approximate and shift by about a day from year to year; the degree of your Sun is definitive. Sub-rulers follow the triplicity method. In the Chaldean method the sequence Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter repeats from 0° Aries, so Aries is Mars / Sun / Venus and Taurus is Mercury / Moon / Saturn.
Frequently asked questions
What is a decan in astrology?
A decan is one of three 10-degree sections of a zodiac sign, giving 36 decans across the zodiac, each roughly ten days long. Every decan keeps its sign's element, modality and ruler but adds a planetary sub-ruler that shades the sign's traits. The system comes from ancient Egyptian star calendars and was absorbed into Hellenistic astrology; it is the main reason two people with the same Sun sign can feel quite different.
How do I find my decan?
Either use your birthday with a decan table (the first decan begins when the Sun enters the sign, the second about ten days later, the third about twenty days later) or, more reliably, read the degree of your Sun in your birth chart: 0° to 9° is the first decan, 10° to 19° the second, 20° to 29° the third. The degree method matters for anyone born within a day of a boundary, since dates shift slightly each year.
What are the Virgo decans?
The first Virgo decan (about 23 August to 2 September) is ruled by Mercury and is the analytical, precise, verbal Virgo. The second (about 3 to 12 September) is sub-ruled by Saturn through Capricorn: disciplined, ambitious, a builder. The third (about 13 to 22 September) is sub-ruled by Venus through Taurus: sensual, patient, artistic, and warmer than the Virgo stereotype. All three remain mutable earth ruled by Mercury.
Do decans change my zodiac sign or personality?
They never change your sign; a third-decan Leo is still a Leo. What they change is emphasis. The first decan is the sign's purest form, the second and third borrow a related planet's tone, so a third-decan Leo carries an Aries edge and a second-decan Scorpio a Pisces softness. Astrologers treat the decan as a refinement of the Sun sign, read alongside the Moon, rising sign and the rest of the chart.
Why are there two systems of decan rulers?
The triplicity method, common in modern astrology, assigns each decan to the three signs of the same element in order, so Aries's decans belong to Aries, Leo and Sagittarius. The older Chaldean method cycles the seven classical planets from Mars at 0° Aries in the order Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter. Both systems agree on the first decan of each sign and differ on the second and third; traditional astrologers use the Chaldean faces as a minor dignity.
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AstraLink content is written by our editorial team, reviewed for astrological accuracy, and refreshed as the sky moves. Interpretations are for reflection and entertainment; they are not medical, legal or financial advice.