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.

Supported House Systems

Placidus

Placidus is the most widely used house system in modern Western astrology worldwide, and it is the default setting in HOSHIDOU. It is a time-based (temporal) system: it divides the time it takes a degree of the ecliptic 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. Because the calculation depends on diurnal motion, houses vary considerably in size with birth latitude and time. 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. Its main caveat is at high latitudes: as you approach the Arctic and Antarctic circles, degrees of the ecliptic that never rise or set break the time-division logic, and the system either fails or produces extreme, distorted house sizes for births above roughly 66 degrees latitude.

Whole Sign

Whole Sign is the oldest house system in the astrological tradition and has seen a strong resurgence alongside renewed interest in Hellenistic and traditional astrology. It is a sign-based (ecliptic) system: the entire sign containing the Ascendant becomes the 1st house, the next sign the 2nd house, and so on, so every house occupies exactly one complete zodiac sign (30 degrees) and house cusps coincide with sign boundaries. Use it when you practice traditional techniques, want houses that are simple to read, or need a system that behaves predictably regardless of birth location. Because the assignment depends only on the Ascendant's sign rather than precise diurnal arcs, Whole Sign remains completely stable at high latitudes and is a reliable choice for polar or near-polar birth places where quadrant systems fail.

Koch

Koch is a time-based (temporal) system, like Placidus, but uses a different calculation: it bases the intermediate cusps on the diurnal arc of the Ascendant degree rather than each cusp's own degree, which tends to produce somewhat different house sizes. It is especially popular among astrologers in German-speaking countries and among practitioners who work with birth-time-rectification techniques. Use it if your training or reference materials follow the Koch convention, or if you specifically want a temporal system that emphasizes the Ascendant's diurnal motion. 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 Koch and Placidus can diverge noticeably even at moderately high latitudes.

Regiomontanus

Regiomontanus is 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. It is the system traditionally favored in horary and classical astrology - the branch that answers specific questions using the chart of the moment. Use it for horary work, traditional practice, or when following older source texts that assume Regiomontanus houses. Because it divides the equator spatially rather than dividing rising times, it remains 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

Campanus is a space-based (spatial) 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, so each house occupies the same spatial extent of sky measured along that reference circle. It appeals to astrologers who value true spatial symmetry in house division and to those exploring the local-space dimension of a chart. Use it when you want houses based on the observer's local sky geometry rather than on time. Like Regiomontanus, it stays mathematically defined at higher latitudes than the temporal systems, but house sizes projected onto the ecliptic grow increasingly distorted and uneven the closer the birthplace is to the poles.

Equal

Equal House is an ecliptic-based system that assigns exactly 30 degrees to each house, measuring from the precise degree of the Ascendant - so if the Ascendant is at 14 degrees Taurus, every cusp falls at 14 degrees of its sign. It is one of the simplest and oldest systems and resembles Whole Sign in that every house is the same size, but the starting point is the exact Ascendant degree rather than the sign boundary. Use it when you want even, predictable houses anchored to the precise Ascendant, or as a stable alternative to quadrant systems. One notable difference from quadrant systems is that the Midheaven does not necessarily fall on the 10th house cusp; instead it floats and is usually shown separately. Because it depends only on the Ascendant degree, Equal House remains fully stable at high latitudes and works reliably for polar birth locations.

Porphyry

Porphyry is the simplest of the quadrant systems. It is an ecliptic-based system that trisects each of the four quadrants formed by the ASC-MC, MC-DSC, DSC-IC, and IC-ASC axes, so each quadrant's ecliptic arc is simply divided into three equal parts. It is a classical system with very straightforward arithmetic, which makes 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. Use it when you want angular houses without the heavier trigonometry of Placidus, Koch, Regiomontanus, or Campanus. Because it only divides the ecliptic arcs between the angles, Porphyry remains 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.