There are over 10 different ways to divide the sky into 12 houses. Each system uses different math and philosophy. Here's a complete guide to help you understand them.
10
House Systems
2000+
Years of History
Placidus
Most Popular
Whole Sign
Oldest System
| System | Polar Safe | Equal Houses |
|---|---|---|
#1Placidus | ||
#2Whole Sign | ||
#3Koch | ||
#4Topocentric | ||
#5Equal House | ||
#6Regiomontanus | ||
#7Campanus | ||
#8Porphyry | ||
#9Alcabitius | ||
#10Morinus |
Placidus de Titis (1603)
Divide TIME - how long each degree takes to travel from horizon to midheaven
Each house cusp is the degree that has completed 1/3, 2/3 of its semi-arc journey from rising to culminating.
Hellenistic astrologers (200 BCE)
Each zodiac sign IS a house - the simplest possible system
The sign containing your Ascendant becomes the 1st house. The next sign is the 2nd house, and so on. No math required beyond finding the Ascendant.
Walter Koch (1962)
Divide the path the Ascendant degree has traveled since rising
Trisects the Ascendant's own journey from horizon to midheaven. The "birthplace" system.
Wendel Polich & A.P. Nelson Page (1961)
Modern refinement of Placidus accounting for exact observer position on Earth's surface
Like Placidus but adjusts for the observer being on the Earth's surface, not at its center.
Hellenistic/Medieval astrologers (100)
Divide the zodiac into 12 equal 30° segments starting from the Ascendant
Start at the Ascendant degree, then each house cusp is exactly 30° further. All houses are exactly 30°.
Johannes Müller (Regiomontanus) (1475)
Divide the celestial equator into 30° segments, then project via great circles
Trisects the celestial equator, then uses great circles through the north and south points to find ecliptic cusps.
Johannes Campanus (Giovanni Campano) (1260)
Divide the prime vertical into 30° segments, then project onto the ecliptic
Uses great circles through the north and south points of the horizon. Space-based rather than time-based.
Porphyry of Tyre (270)
Trisect each quadrant of the chart evenly along the ecliptic
Take the four angles (ASC, IC, DSC, MC) and divide each quadrant into three equal parts. Simple trisection.
Al-Qabisi (Alcabitius) (960)
Trisect the semi-arcs projected onto the celestial equator
Divides the time it takes for a point to rise to culminate, projected onto the equator. Arabic tradition.
Jean-Baptiste Morin (Morinus) (1661)
Divide the celestial equator equally, project to ecliptic without latitude adjustment
Like Regiomontanus but ignores geographic latitude entirely. Pure equator-to-ecliptic projection.
None is objectively "correct" - they're all valid mathematical models. Different systems divide the sky differently, like different ways to slice a pie. The "best" one depends on your astrological tradition and what you're trying to learn about a chart.
All systems agree on the Ascendant (Rising sign) and Midheaven - these are fixed astronomical points. What changes is where the intermediate house boundaries fall, which can shift planets between houses.
Whole Sign is the simplest to understand - each sign equals one house. Placidus is the most popular if you want to match what most apps show. Try both and see which resonates with your experience.
Systems like Placidus divide TIME (how long each degree takes to travel across the sky). Near the poles, some degrees never rise or set, making time-based division mathematically impossible. Space-based systems like Whole Sign or Campanus don't have this problem.
Yes! In most astrology apps, you can select your preferred house system. Your planets don't move - only the house boundaries change, which may shift which houses some planets fall in.
Get your personalized birth chart and explore how different house systems change your planet placements.
Generate My Free Chart