House Systems

House Systems. A house system is a method for dividing the chart into its twelve houses. All systems start from the same birth time and place, and most agree on the Ascendant and Midheaven, but they draw the house cusps differently. This means a planet can land in one house under one system and an adjacent house under another, so the choice of system can change a reading. Whole Sign is the oldest system, used in Hellenistic astrology and popular again today. Each house is exactly one sign, with the rising sign forming the entire first house. It is simple and keeps signs and houses aligned. Placidus is the most common system in modern Western astrology. It divides the houses by time, based on how long degrees take to rise, which produces houses of unequal size and can distort at far northern or southern latitudes. Equal House gives every house a uniform thirty degrees measured from the Ascendant. Other systems such as Koch, Porphyry, Campanus, and Regiomontanus use their own geometry. There is no single correct system. Many astrologers choose one that fits their tradition and stay consistent with it.