House systems are methods of dividing a horoscope into twelve sectors. While all use zodiacal or horizon-related reference points, they do not allocate house boundaries in the same way. This means a planet can move from one house to another when the same chart is recalculated under a different system, without its zodiac sign changing.
Whole Sign and Equal House systems
Whole Sign Houses assigns an entire zodiac sign to each house, beginning with the Ascendant’s sign as the first house. Equal House begins the first house at the Ascendant’s exact degree, with subsequent cusps spaced 30 degrees apart. These systems are geometrically straightforward, but they handle house cusps and the Midheaven differently.
Placidus and quadrant houses
Placidus is a widely used time-based quadrant system. Other quadrant approaches include Regiomontanus, Campanus and Koch; each has its own calculation rules. At very high latitudes some systems can become difficult or impossible to calculate in ordinary form. Authors should identify the system behind a chart instead of mixing interpretations from incompatible calculations.
Choosing a system for interpretation
The house system is a methodological choice, not an objective personality result. Readers can compare whole-sign and quadrant approaches against a consistent set of interpretive principles. Avoid changing systems solely to force a preferred interpretation; first confirm the birth time, location, angles and planetary positions.
Continue exploring
For the wider context, return to Astrology Houses. Related topic pages in this section expand these ideas with placement-specific interpretations.