Decan in Astrology

A decan (or decanate) divides each 30° zodiac sign into three equal 10° sections. Each section carries its own sub-ruler and slightly different flavor within the sign's overall character. Decans add a layer of nuance to any planet's exact degree placement within a sign.

How Decans Work

Each sign has three decans:

• First decan: 0°–9°59' — purest expression of the sign
• Second decan: 10°–19°59' — flavored by the next sign in the same element
• Third decan: 20°–29°59' — flavored by the third sign in the same element

The Modern Decan System (Same-Element Rulers)

In the most widely used modern system, each decan is associated with the signs of the same element in order:

Aries (Fire):

• First decan (0°–9°): Aries sub-tone (Mars)
• Second decan (10°–19°): Leo sub-tone (Sun)
• Third decan (20°–29°): Sagittarius sub-tone (Jupiter)

Taurus (Earth):

• First decan (0°–9°): Taurus sub-tone (Venus)
• Second decan (10°–19°): Virgo sub-tone (Mercury)
• Third decan (20°–29°): Capricorn sub-tone (Saturn)

Traditional Chaldean Decan System

Traditional astrology uses a different assignment — the Chaldean order of planets (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon) cycling through the decans. This system is used in horary, Hellenistic, and some traditional natal work.

What Decans Mean in Practice

A planet at 2° Scorpio (first decan, purest Scorpio) expresses pure Scorpionic intensity. The same planet at 22° Scorpio (third decan, Cancer sub-tone) carries Scorpionic themes but with an emotionally nurturing, protective overlay — intensity tempered by Cancer's sensitivity.

Decans are most commonly applied to the Sun (giving the three "types" within each sign in decan-based horoscope content) but can be applied to any planet.

Related Terms

• Dignity
• Natal Chart
• House Systems
• Sun
• Ascendant

Calculate your free birth chart to find your Sun's decan and its sub-ruler.