Placidus divides the sky into 12 houses of different sizes based on time, and it is the most used house system in modern Western astrology. Whole Sign makes each house exactly one sign, starting with the rising sign, and it is the oldest system, used in Hellenistic astrology about 2,000 years ago. The two agree on your rising sign but can put a planet in different houses, most often when it sits near a house cusp.
How do the two systems compare?
| Placidus | Whole Sign | |
|---|---|---|
| House size | Varies, often 20° to 40° | Always 30° |
| First house starts at | The exact degree of the Ascendant | 0° of the rising sign |
| Midheaven | Always the 10th house cusp | Can fall in the 9th, 10th or 11th house |
| Works at all latitudes? | No, it fails near the poles | Yes |
| Most used in | Modern Western astrology | Hellenistic and Vedic astrology |
Why can a planet change house between the two?
In Placidus, houses start at exact degrees that depend on your birth time and latitude, so a house can be much wider or narrower than a sign. In Whole Sign, every planet in your rising sign is in the 1st house, every planet in the next sign is in the 2nd, and so on. A planet a few degrees before a Placidus cusp may move one house over in Whole Sign.
Why does Placidus fail near the poles?
Placidus divides the time each degree takes to rise. Above about 66° latitude, near the Arctic and Antarctic circles, some degrees of the zodiac never rise or never set for part of the year, so the division breaks down. Whole Sign does not have this problem.
Which system do we use?
Our report uses Placidus, the most common choice, and switches to Whole Sign above 66° latitude, saying so in the report. Both are valid; if a planet sits within a few degrees of a cusp, it is worth reading the next house too. Our methodology page lists every setting we use.
Read more about the 12 houses, or see your own chart with the natal chart report for 20 crystals (about £1).