Placidus — the default house system
Placidus is the house system the public calculator sends as houseSystem PLACIDUS. House cusps depend on the Ascendant, the midheaven, and the birth latitude. They are not the twelve equal signs.
Last updated
The ephemeris maps the name PLACIDUS to the Swiss Ephemeris house code P. WHOLE_SIGN maps to W, EQUAL to E, and KOCH to K. Anything else is rejected. The website does not expose a picker; it always posts PLACIDUS so every public chart is comparable.
In Placidus, house sizes are unequal. A high latitude can make some houses very large. Whole sign, by contrast, gives each house one entire sign starting from the rising sign. Those two charts for the same birth will not list the same house number for a planet. When this site says “house 7” it means the Placidus seventh house, not “the descendant’s sign” in the abstract.
Signs and houses answer different questions. The sign pages divide the ecliptic into twelve 30° windows that ignore the horizon. Placidus divides the local sky. A planet in Aries can fall in any house. Reading a sign page as a house page mixes the two systems.
Whole sign would put every planet in Aries into house 1 when Aries is rising, regardless of whether the planet is at 1° or 29°. Placidus does not. A planet at 29° Aries can fall in house 2 while a planet at 1° Aries is still in house 1, if both cusps sit inside Aries. That is normal at mid latitudes and common at high ones. The public form locks PLACIDUS so a house number on this site always means that unequal system.
Questions
What house code is sent?
PLACIDUS, Swiss Ephemeris code P. WHOLE_SIGN, EQUAL, and KOCH exist on the service and are not what the public form submits.
Are Placidus houses 30° each?
No. The signs are 30° each. Placidus houses vary with latitude and time. Their cusps are part of the chart response, not of the sign pages.
Related pages
Sources
Sources: longitudes from the Swiss Ephemeris evaluating JPL Development Ephemeris 431. Aspect orbs (8°, and 6° for the sextile) are AstroStella constants, not a field inside DE431.
AstroStella is an entertainment service. These pages describe the calculation, not medical, legal, or financial advice.