Astrology · House Systems · Comparison

House Systems Compared

Every chart needs a way to divide the sky into twelve houses — and astrologers have never fully agreed on how. Here's what each major system actually does, and why the same birth data can put a planet in two different houses depending on the system.

Why this matters: the planets' positions never change based on house system — only which house each one falls into. There is no single "correct" system; each comes from a different mathematical logic for dividing time and space.

Section 01

Sign-Based vs Quadrant-Based

Nearly every house system falls into one of two families. Sign-based systems (Whole Sign, Equal) ignore the exact geometry of the birth moment beyond the Ascendant's sign, and simply assign whole 30° zodiac signs to houses. Quadrant-based systems (Placidus, Koch, Regiomontanus, Campanus, Topocentric) start from the four angles — Ascendant, Midheaven, Descendant, IC — actually calculated for the birth moment and location, then divide the space between them, producing houses of unequal size that vary by latitude.

A third, older approach — Porphyry — is a simple hybrid: it uses the real quadrant angles but divides each quadrant into three equal parts by degree, without the more complex trigonometry of later systems.

Section 02

Every Major System

Whole Sign
Ancient · Sign-Based
The oldest known system, used throughout Hellenistic astrology. Whatever sign the Ascendant falls in becomes the entire 1st house.
Placidus
Quadrant · Most Common
The default in most modern software. Uses "trisection of time" to divide each quadrant, producing uneven house sizes.
Koch
Quadrant · Birthplace System
Similar to Placidus but based on the birthplace's local horizon geometry. Undefined above the polar circles.
Equal House
Sign-Based
Starts from the exact Ascendant degree and adds 30° repeatedly. Reliable at any latitude.
Porphyry
Quadrant · Simple
Uses the real angles, divides each quadrant into three equal parts by degree — no trigonometry involved.
Regiomontanus
Quadrant · Medieval Standard
Divides the celestial equator into equal segments, then projects onto the ecliptic. Still favoured by traditional astrologers.
Campanus
Quadrant · Prime Vertical
Divides the prime vertical into equal segments — a more explicitly spatial approach than time-based systems.
Topocentric
Quadrant · Modern
Developed to approximate Placidus more reliably at high latitudes, based on the observer's exact position.
Section 03

Comparison at a Glance

Whole Sign & Equal House — always exactly 30° houses, no issues at any latitude. Porphyry, Regiomontanus & Campanus — uneven house sizes, but stable with no undefined zones. Placidus & Koch — uneven, can be extreme, undefined inside or near the polar circles. Topocentric — uneven, more stable than Placidus/Koch at high latitudes.

Section 04

Which System Should You Use?

There is no scholarly consensus that one system is objectively correct — the choice is a matter of tradition, lineage and practical fit. What matters most is picking one system, learning it well, and staying consistent so your pattern-recognition across many charts stays reliable.

Traditional / Hellenistic Practice
→Whole Sign is historically correct and the modern default since the 1990s revival
→Simplest to calculate by hand
Modern Psychological Practice
→Placidus remains the software default
→The most widely taught system in 20th-century Western astrology
High-Latitude Birth
→Avoid Placidus and Koch — they break down near the polar circles
→Whole Sign, Equal, Porphyry, Regiomontanus and Campanus stay stable
Planet Near a House Cusp
→Check the placement across two or three systems
→Treat disagreement as informative, not a problem to resolve
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