House Systems in Astrology
Different methods for dividing the birth chart into twelve houses — each producing different house sizes and cusp degrees.
The twelve houses in an astrological chart can be calculated using several different systems. Each method divides the ecliptic or celestial sphere differently, resulting in houses of varying sizes. The choice of house system can shift which planets fall in which houses, so understanding the options helps you interpret charts more accurately.
Placidus
The most widely used system in Western astrology. Placidus divides the chart based on the rotation of the Earth, creating unequal house sizes that vary by latitude. It works best for mid-latitudes but can produce very large or small houses near the poles.
Best for: Psychological and modern Western astrology
Whole Sign
One of the oldest systems, originating in Hellenistic astrology. Each house corresponds to an entire sign — the Ascendant sign becomes the first house, the next sign the second, and so on. All houses are equal in size at exactly 30 degrees.
Best for: Traditional, Hellenistic, and Vedic-influenced readings
Equal House
The Ascendant degree begins the first house, and each subsequent house starts exactly 30 degrees later. This creates equal-sized houses like Whole Sign but anchored to the exact Ascendant degree rather than the whole sign.
Best for: Beginners and those preferring simplicity
Koch
A time-based system developed in the 20th century. Koch uses the birth time and location to calculate houses based on how long each degree of the ecliptic stays above the horizon. It produces houses of unequal size and is sensitive to geographical latitude.
Best for: Event-based and predictive astrology
Campanus
Campanus divides the prime vertical (the great circle from East to West through the Zenith) into equal parts. This creates a geometric system rooted in the observer's local sky rather than the ecliptic. Houses can vary significantly in size.
Best for: Spiritual and esoteric astrology
Regiomontanus
Developed in the 15th century, Regiomontanus divides the celestial equator into equal parts and projects them onto the ecliptic. It was historically used in horary astrology and was the dominant system in Europe before Placidus became widespread.
Best for: Horary and traditional medieval astrology
Which House System Should You Use?
There is no single correct house system. Most Western astrologers default to Placidus because it is built into the majority of chart software and has the largest body of literature. Whole Sign is gaining popularity due to its simplicity and its roots in Hellenistic tradition.
The best approach is to study your own chart using multiple systems and notice which one resonates most with your lived experience. Many professional astrologers use Placidus for natal work and switch to Whole Sign for timing techniques.