House System

House systems are competing methods for dividing the chart into twelve houses. Different systems place planets in different houses, and there is no settled astrological consensus on which is correct.

All house systems agree on the Ascendant (the eastern horizon at birth) and the Midheaven (the highest point in the chart). They disagree on how to draw the boundaries of the houses between these angles. Whole-sign houses, the oldest system, take the rising sign as the entire 1st house, the next sign as the entire 2nd house, and so on. The Ascendant is a point within the 1st house, not its boundary. This system is used in Hellenistic and most Vedic astrology and has had a major revival in modern Western practice. Placidus houses, the most common in 20th-century Western astrology, divide the diurnal arc (the path the Sun takes between the eastern and southern angles) into thirds and project these divisions onto the ecliptic. This is mathematically complex and produces houses of unequal size; at high latitudes (above the Arctic Circle), Placidus breaks down entirely. Other systems include Koch, Equal House (each house exactly 30 degrees from the Ascendant), Regiomontanus, Campanus, Porphyry, and more. Each has historical and mathematical justification; none can be empirically validated as 'correct.' The practical consequence: a planet placed near a house cusp may fall in different houses depending on the system used. A reading that uses Placidus may put your Venus in the 6th house; a reading that uses whole sign may put it in the 5th. Both readings will sound plausible because both are working with traditional interpretive frameworks; this does not mean both are equally accurate, only that astrology has no settled answer to the question. In this reading: [the system used should be stated transparently — the project's engine uses Placidus by default, with whole-sign available as an alternate].

Not: A house system is not arbitrary, but it is conventional. The choice of system is a methodological decision, not a measurement. Practitioners who insist that one system is the 'true' one and all others are wrong are overstating what the evidence supports.

There is no empirical basis for choosing one house system over another. Disagreements between traditions are real and unresolvable from outside the astrological framework itself. The best a reading can do is be transparent about which system it uses and acknowledge that placements near house cusps may fall in different houses under different systems.