What a house system actually is
A house system is a rule for dividing your natal chart into twelve sectors called houses. Each house stands for a field of life: self, money, home, work, partnership, career, and so on.
Your planets do not move when you switch systems. Their zodiac positions come straight from the sky and stay identical. Only the house lines shift, and with them the house a planet is said to occupy.
That is why the same planet can be 'in the tenth house' on one chart and 'in the eleventh' on another. Both are correct inside their own system. This tool shows you all of them at once, so the choice is yours to see and to make.
How the five systems differ
Every system starts from the same two anchors. The Ascendant is the degree rising in the east at your birth. The Midheaven is the highest point the sky reaches. Both come from your birth time and place, not from any rule.
A quadrant system keeps both anchors on their cusps. It pins the Ascendant to the first house and the Midheaven to the tenth, then fills in the space between them. Porphyry, Regiomontanus and Campanus are three quadrant systems.
They differ only in how they divide that space. Porphyry cuts the gap between the angles into equal thirds. Regiomontanus divides the celestial equator into twelve equal parts. Campanus divides the prime vertical, a different great circle.
Two systems here do not keep both anchors. Equal houses step thirty degrees from the exact Ascendant, so the Midheaven drifts off its cusp. Whole-sign gives one zodiac sign to each house, so both angles drift. Together the five span the whole design space.
What you get back
Enter your birth data and the tool re-houses every planet across all five systems, returning:
- All twelve cusps for each system, lined up side by side.
- The house of every body under each system.
- A count of how many planets change house between systems.
- The exact degree of your Ascendant and Midheaven.
- A plain note on which systems keep your angles and which let them drift.
Which system should you use?
There is no single right answer, and honest sources say so. Each system is a different, self-consistent geometry. Pick one, learn it, and stay with it, so your readings mean the same thing from chart to chart.
Most software defaults to Placidus. We do not compute it here, because its cusps come from an iterative time-based solve. Instead we show five systems whose cusps we can verify exactly, and we discuss the time-based ones in words.
If you read traditional or Hellenistic astrology, use Whole-sign. It is the oldest system and never intercepts a sign. If you want your angles pinned on a simpler grid, use Equal. For a quadrant chart without Placidus, Porphyry is a robust middle choice.
Watch the planets that shift houses. A body that changes house is sitting near a cusp. Its degree is certain; only its label is soft. Read those planets by sign and aspect first, and treat the house as a useful hint.
A worked example: one London chart, five frames
We verify against a fixed chart: 1 January 2000 at 17:30 UT in London. The Ascendant is 28.8 degrees of Cancer and the Midheaven is 3.3 degrees of Aries. Across these five systems, ten of ten bodies change house at least once.
Saturn shows the biggest stakes. At 10.4 degrees of Taurus it sits in the eleventh house under Whole-sign and Campanus, but in the tenth under Equal, Porphyry and Regiomontanus. Friends or career, decided only by the system you pick.
Equal is the odd one out twice more. Jupiter and Mars each hold the house the quadrant systems give them, yet Equal slides both back one, because Equal lets the Midheaven line drift off the tenth cusp.
Whole-sign is the outlier at the sign edges. Uranus and Neptune fall in the eighth under Whole-sign but in the seventh under all four other systems. The Moon alone flips, landing in the fifth under three systems and the fourth under two.
The cusps make it plain. Your second cusp runs from 0.0 degrees of Leo in Whole-sign to 25.8 in Campanus, a gap of nearly a whole sign. Campanus even pulls the fifth cusp back to 29.8 degrees of Libra, one sign earlier.
The five systems at a glance
The table below is the whole design space in one view. The two outer systems break the angles; the three inner ones are quadrant systems that agree on every angle and differ only in between.
| System | Family | Keeps both angles | How it divides |
|---|---|---|---|
| Whole Sign | Sign-based | No | One zodiac sign per house |
| Equal | Angle from ASC | No | Thirty degrees from the Ascendant |
| Porphyry | Quadrant | Yes | Equal thirds between the angles |
| Regiomontanus | Quadrant | Yes | Equal parts of the celestial equator |
| Campanus | Quadrant | Yes | Equal parts of the prime vertical |
What this tool does not claim
Two popular systems are missing on purpose. Placidus and Koch build their cusps from an iterative solve of a planet's daily arc. We can describe that method, but we will not print house numbers we cannot pin to the degree.
Every angle depends on your birth time. The Ascendant moves about one degree every four minutes, and the Midheaven a little slower. A guessed time can drag a cusp across a planet and rewrite the whole table.
A house is a label, not a force. The sky holds each planet at its degree whether or not a line runs beneath it. The systems are useful, and they are human conventions. Hold the astronomy firmly and the meaning lightly.
Our method in one line
Positions come from sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine). Our reference frame is Porphyry quadrant houses (whole-sign available on every chart). The comparison recomputes only the cusp lines, so every planet keeps one identical longitude across all five systems.
The three quadrant systems are checked to agree on all four angles, and the Regiomontanus cusps are checked against the thirty-degree equator grid. Every worked-example figure is reproduced by an automated probe. Reviewed by Dr. Amara Osei, Astronomy Reviewer.
Step by step
- 1
Enter your birth data
Add your birth date, exact time and place. The two anchors that hold up every house system come from these facts alone.
- 2
Scan the cusp table
Read all twelve cusps for each system side by side, and see how far the same house line travels from one system to the next.
- 3
Find your shifting planets
Look at the bodies that change house. Each one sits near a cusp, so its house depends on the system you favour.
- 4
Pick one and commit
Choose a single system for your reading practice.
Tip — Consistency matters more to your readings than which system you choose.
Frequently asked questions
- Why do my planets change houses between systems?
- Because the house lines move, not the planets. Each system draws the twelve cusps by a different rule, so a planet sitting near a boundary can fall on either side of it. Its zodiac degree stays fixed; only the house label shifts.
- Which house system is the most accurate?
- None is more accurate than another, and no serious source claims otherwise. They are different geometries, each internally consistent. The accuracy belongs to the astronomy, which is identical in every row here. Pick a system, learn it well, and keep using it.
- Why is Placidus not one of the systems shown?
- Placidus builds its cusps from an iterative solve of each planet's daily arc above and below the horizon. We can describe that method in words, but we could not anchor it to a reference table we trust to the degree. So we show five systems we can check exactly.
- Do the Ascendant and Midheaven move too?
- The Ascendant and Midheaven are fixed by your birth time and place, so the points themselves never move. What changes is whether they land on a house cusp. The three quadrant systems pin both to their cusps, while Equal and Whole-sign let the Midheaven drift off its line.
- Which system should a beginner start with?
- Whole-sign is the simplest and the oldest, and it is what most traditional and Hellenistic texts assume. Equal houses come next, keeping your Ascendant while staying easy to read. Start with one, then explore the quadrant systems once house rulerships feel natural.
- Does this tool store or upload my birth data?
- Calculations run entirely in your browser. Your birth data is never uploaded, never stored on a server, and never shared. Every house calculation runs on the spot inside your browser, and nothing you enter is sent to or kept on any server.
Written by
Elena Marchetti
Founder & Staff Astrologer
Methodology reviewed by
Dr. Amara Osei
Astronomy Reviewer
Published 2026-10-02 · Updated 2026-10-02 · Calculated with sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine)