⚙️ House Systems Explained
Why Are There Different House Systems?
All house systems agree on two points: the Ascendant (eastern horizon) and the Midheaven/MC (highest point). Where they disagree is how to divide the space between these points into twelve houses. This has been debated for over two thousand years, and no single system has been universally adopted.
XiNiS supports 10 house systems. Here is what makes each one unique.
Placidus
The most widely used system in Western astrology today. Placidus divides the sky based on time — specifically, the time it takes for each degree of the ecliptic to travel from the horizon to the meridian. This creates unequal house sizes that vary with latitude.
Best for: General natal chart work. The default choice for most modern Western astrologers.
Limitation: Breaks down at extreme latitudes (above ~66°) where some degrees never rise or set.
Whole Sign
The oldest known house system, used in Hellenistic astrology. Each house is simply one entire zodiac sign, starting from the sign of the Ascendant. If your Ascendant is in Leo, the entire sign of Leo is your 1st house, Virgo is your 2nd, and so on.
Best for: Simplicity and clarity. Favored in traditional and Hellenistic astrology. Gaining significant popularity in modern practice.
Koch
Similar to Placidus but uses the birth location’s meridian as the starting reference. Koch divides the diurnal arc of the Ascendant degree into equal segments.
Best for: Practitioners who prefer a time-based system with a different mathematical approach than Placidus.
Equal
Starting from the exact Ascendant degree, each house spans exactly 30°. Simple and symmetric, but the MC may fall in different houses rather than always on the 10th cusp.
Best for: High-latitude locations where Placidus and Koch become distorted. Also popular in Vedic astrology adaptations.
Campanus
Divides the prime vertical (the great circle passing through the zenith and east/west points) into twelve equal 30° arcs, then projects them onto the ecliptic.
Best for: Astrologers focused on the local space perspective. Emphasizes the spatial experience of the observer.
Regiomontanus
Divides the celestial equator into twelve equal 30° segments, then projects them onto the ecliptic through the north and south points of the horizon.
Best for: Horary astrology. This was the standard system in medieval European astrology.
Porphyry
One of the simplest quadrant systems. Takes the arcs between the four angles (ASC, IC, DSC, MC) and trisects each one equally. This creates unequal houses, but the math is straightforward.
Best for: A balanced middle ground — more nuanced than Equal or Whole Sign, simpler than Placidus.
Morinus
Divides the celestial equator into twelve equal parts starting from the RAMC (Right Ascension of the MC), then projects onto the ecliptic. Notably, the Ascendant and MC may not fall exactly on house cusps.
Best for: Astrologers interested in a purely equatorial framework, decoupled from the horizon.
Topocentric
Developed by Polich and Page in the 1960s. Mathematically very close to Placidus but uses a different geometric rationale — based on the observer’s actual position (topocentric = from a point on Earth’s surface). In practice, cusp positions differ from Placidus by less than 1° in most cases.
Best for: Those who want a Placidus-like system with a stronger theoretical foundation.
Alcabitius
An ancient system popular in medieval Arabic astrology. Divides the diurnal arc of the Ascendant into three equal parts for houses above the horizon, and the nocturnal arc for houses below.
Best for: Practitioners of traditional or medieval astrology methods.
Which System Should You Use?
There is no objectively “correct” house system. Most modern Western astrologers use Placidus by default. Whole Sign has seen a major revival and works especially well for beginners. The best approach is to try different systems with your own chart and see which one resonates most with your experience.
In XiNiS, you can switch between all 10 systems instantly to compare how your chart shifts.