House Systems in Astrology

House systems are the different mathematical methods used to divide the natal chart's 360° wheel into 12 houses. Because there are multiple valid geometric approaches to this division, different systems produce different house cusp positions — which can place the same planets in different houses and assign different signs to different life areas.

The Major House Systems

Placidus

The most widely used system in modern Western astrology. The Ascendant is the 1st house cusp; all other house cusps are calculated based on time divisions of the space between the Ascendant and Midheaven. At extreme latitudes (above 60°N or S), Placidus can produce very distorted house sizes.

Whole Sign

The oldest system, used in Hellenistic astrology and experiencing a major revival. The entire sign containing the Ascendant becomes the 1st house. Every house is exactly one 30° sign — no partial signs, no distortion at high latitudes. Widely used in ancient timing techniques (profections, solar returns).

Equal House

The Ascendant degree is the 1st house cusp; each subsequent house cusp is exactly 30° later. Simple and undistorted. The Midheaven is not necessarily a house cusp in this system.

Koch

Similar to Placidus but uses a different calculation method for house cusps. Popular in Germany and some parts of Europe.

Regiomontanus

Divides the celestial equator equally and projects onto the ecliptic. Historically significant; popular in horary astrology.

Which System to Use

There's no single correct answer. Most astrologers recommend:

• Placidus: For modern psychological and natal interpretation
• Whole Sign: For Hellenistic techniques, high-latitude births, timing
• Equal House: For clarity and simplicity, especially when learning

The planets, signs, and aspects remain identical across all systems — only house placements change.

Intercepted Signs

In Placidus and some other systems, intercepted signs occur — a sign falls entirely within a house without ruling any house cusp. These intercepted signs carry special interpretive significance (see: Intercepted Signs).

Related Terms

• Ascendant
• Natal Chart
• 1St House
• Midheaven
• Imum Coeli

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