House System

A house system is the method used to divide the horoscope circle into 12 houses. Different house systems place the house boundaries (cusps) at different degrees, which can change which house a planet falls in. HOSHIDOU supports seven house systems.

This example uses Placidus, HOSHIDOU’s default house system.

Supported house systems

Placidus

• Method. A time-based (temporal) system. It divides the time a degree of the ecliptic takes to rise from the horizon to the meridian into equal parts, then projects those time divisions back onto the ecliptic to set the house cusps.
• Use it when. You want maximum compatibility with the literature. The vast majority of books, software, and online resources assume Placidus, so it is the easiest system to cross-reference while you learn. It is the default in HOSHIDOU.
• Caveat. At very high latitudes (above roughly 66°), degrees of the ecliptic that never rise or set break the time-division logic. The system either fails or produces extreme, distorted house sizes near the polar circles.

Whole Sign

• Method. A sign-based (ecliptic) system. The entire sign containing the Ascendant becomes the 1st house, the next sign the 2nd house, and so on. Every house occupies one complete zodiac sign (30°) and house cusps coincide with sign boundaries.
• Use it when. You practice traditional or Hellenistic techniques, want houses that are easy to read, or need a system that behaves predictably regardless of birth location.
• Caveat. Because the assignment depends only on the Ascendant’s sign rather than precise diurnal arcs, Whole Sign stays completely stable at high latitudes — a reliable choice for polar or near-polar birth places where quadrant systems fail.

Koch

• Method. A time-based system like Placidus, but it bases the intermediate cusps on the diurnal arc of the Ascendant degree rather than each cusp’s own degree. This tends to produce somewhat different house sizes.
• Use it when. Your training or reference materials follow the Koch convention, or you specifically want a temporal system tied to the Ascendant’s diurnal motion. It is especially popular among astrologers in German-speaking countries and among practitioners who work with birth-time-rectification techniques.
• Caveat. Like Placidus, Koch degrades badly near the poles. It relies on the same rising-time geometry, so it becomes unreliable or undefined at high latitudes, and the two systems can diverge noticeably even at moderately high latitudes.

Regiomontanus

• Method. A space-based (spatial) system. It divides the celestial equator into 12 equal arcs and projects those divisions through great circles onto the ecliptic to determine the house cusps.
• Use it when. You work in horary or classical astrology — the branch that answers specific questions using the chart of the moment — or you follow older source texts that assume Regiomontanus houses.
• Caveat. It stays mathematically defined at much higher latitudes than Placidus or Koch, though the intermediate houses can still become quite uneven as you approach the poles.

Campanus

• Method. A space-based system that divides the prime vertical — the great circle running east-west through the zenith — into 12 equal arcs, then projects them onto the ecliptic. Each house occupies the same spatial extent of sky measured along that reference circle.
• Use it when. You value true spatial symmetry in house division, or you are exploring the local-space dimension of a chart.
• Caveat. Like Regiomontanus, it stays mathematically defined at higher latitudes than the temporal systems, but house sizes projected onto the ecliptic grow increasingly distorted the closer the birthplace is to the poles.

Equal

• Method. An ecliptic-based system that assigns exactly 30° to each house, measured from the precise degree of the Ascendant. If the Ascendant is at 14° Taurus, every cusp falls at 14° of its sign.
• Use it when. You want even, predictable houses anchored to the precise Ascendant, or as a stable alternative to quadrant systems.
• Caveat. The Midheaven does not necessarily fall on the 10th house cusp; instead it floats and is usually shown separately. Because the system depends only on the Ascendant degree, it stays fully stable at high latitudes.

Porphyry

• Method. The simplest of the quadrant systems. It trisects each of the four quadrants formed by the ASC-MC, MC-DSC, DSC-IC, and IC-ASC axes, dividing each quadrant’s ecliptic arc into three equal parts.
• Use it when. You want angular houses without the heavier trigonometry of Placidus, Koch, Regiomontanus, or Campanus. The classical arithmetic is straightforward, making it an accessible entry point for those moving from Whole Sign toward quadrant-based interpretation while still keeping the Ascendant and Midheaven on the 1st and 10th cusps.
• Caveat. Because it only divides the ecliptic arcs between the angles, Porphyry stays defined and comparatively stable at high latitudes — the quadrants can become very unequal in size near the poles, but the system never fails outright the way Placidus and Koch do.

How to change

To change the house system, open Settings, then select the House System dropdown and choose the system you want. Your selection takes effect immediately on all charts.

What it affects

The house system setting applies to every chart type in HOSHIDOU — Single Wheel, Triple Wheel, synastry, and composite. Changing the system shifts house cusp positions, which may reassign planets to different houses and update the house cusp table.

If you’re unsure which system to pick, leave it on Placidus. Most astrology books and online resources use Placidus, making it the easiest choice while you’re learning. For a quick overview of what each house actually means, see Houses. The house system can also be changed as part of a calculation preset.