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Whole Sign vs Placidus: which house system should you use?
By the Hourwyn team
Placidus and Whole Sign are two ways of dividing a birth chart into twelve houses. Placidus divides by time, so its houses come out unequal in size. Whole Sign gives each house exactly one sign. Both start from the same rising sign, but a planet can land in a different house depending on which one is used. Neither can be proven right, so use one consistently.
The two systems side by side
| Placidus | Whole Sign | |
|---|---|---|
| How it divides the sky | By the time each degree takes to travel between the horizon and the top of the sky, cut into thirds | One whole sign per house |
| House size | Unequal, and more so far from the equator | 30° each |
| First house starts | At the exact rising degree | At 0° of the rising sign |
| Midheaven | Always the start of the tenth house | Can fall in another house, often the ninth or eleventh |
| History | Named for the 17th-century mathematician Placidus de Titis | The oldest known system, used in Hellenistic astrology |
| Far north or south | Not defined beyond about 66° of latitude | Works at any latitude |
Why a planet changes house
Take a chart with the Ascendant at 25° of Leo and a planet at 12° of Leo. In Whole Sign the first house is all of Leo, so the planet is in the first house. In Placidus the first house begins at 25° of Leo, and a planet at 12° has already risen above the horizon, which puts it in the twelfth house.
The later in its sign the Ascendant falls, the more planets change house between the two systems. With an Ascendant in the first few degrees of a sign the two agree far more often.
What stays the same
- The sign and degree of every planet.
- Every aspect between planets.
- The Ascendant and the Midheaven themselves.
Houses are a convention for dividing the sky. They are not a measurement, so no observation can settle which system is correct. This is also the most common reason a chart looks different on two websites.
How to choose
- Following a book, a course or an astrologer? Use the system they use, or their house descriptions will not line up with your chart.
- Born far north, in Alaska, northern Scandinavia or similar latitudes? Whole Sign avoids the distortion Placidus has there.
- No strong reason either way? Placidus is the default on most Western astrology sites, so it is the easiest to compare.
- Curious? Look at both and note which planets change house. Those are the placements to hold loosely.
Common questions
Which house system is most accurate?
Neither can be shown to be more accurate. Both are calculated exactly. They are different rules for dividing the same sky, and astrologers choose by tradition and preference.
Do my signs change with the house system?
No. Planets keep their signs and degrees in every house system. Only the house numbers change.
What are intercepted signs?
In Placidus a house can be wide enough to swallow a whole sign, so that sign touches no house border. This cannot happen in Whole Sign, where every sign is one house.
What is the Equal house system?
A third option: twelve houses of 30° each, counted from the exact rising degree instead of from the start of the rising sign.
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Sources
- House (astrology): systems of house division. Wikipedia.
The guides are written by Hourwyn with the help of AI tools. Astronomical and historical facts are checked against the sources listed under each guide. Astrology is described as a tradition and offered for entertainment. Nothing here is medical, financial, legal or psychological advice.