Placidus
The most common system in modern Western astrology. It divides the time it takes each degree to travel from horizon to meridian into thirds. Houses vary in size, and the system breaks down near the poles (above about 66° latitude).
Whole Sign
The oldest system: the whole sign on the ascendant is the 1st house, the next sign the 2nd, and so on. Every house is exactly one sign. Popular with Hellenistic and traditional astrologers.
Which Should You Use?
Try both in our calculator and see which descriptions resonate. Many astrologers use Whole Sign for houses but still note the Placidus angles (ASC and MC).
Other Systems
Koch, Equal, Porphyry, Campanus and Regiomontanus are also used. Our calculator offers the two most popular.
Why Planets Change Houses
Quadrant systems like Placidus divide the sky by time and space, so houses have unequal sizes; Whole Sign uses one sign per house. A planet late in a sign can therefore be in the 10th house in Placidus and the 11th in Whole Sign. The sign and aspects don't change — only the life area emphasized.
Comparison Table
| System | How houses are divided | House sizes | Best known for |
|---|---|---|---|
| Placidus | Time for degrees to rise to the MC | Unequal | Modern Western standard |
| Whole Sign | One whole sign per house | Equal (30°) | Hellenistic, Vedic |
| Equal | 30° from the Ascendant degree | Equal | Simple, works at all latitudes |
| Koch | Birthplace-based time division | Unequal | Popular in Germany |
| Porphyry | Trisects each quadrant | Unequal | Oldest quadrant system |
High Latitudes
Above about 66° latitude (northern Scandinavia, Alaska, Iceland) some ecliptic degrees never rise, so Placidus and Koch can't be computed. Our calculator automatically switches to Whole Sign in those cases and tells you.
Our Recommendation
Beginners can start with Placidus because most books and websites use it. If house descriptions don't resonate, switch to Whole Sign in the calculator settings and compare.
Want your chart read by an astrologer?
Start with PsychicBook: 50% off + 10 free minutes for new customers.