House system
A house system is a method for dividing the chart into twelve houses, and the common ones disagree because they divide different things: space, time or the ecliptic itself.
Placidus divides time and is the modern default; whole sign gives each house a whole sign and is the oldest and the Hellenistic standard; Koch, Regiomontanus, Campanus and others each carry their own logic.
Near the equator the systems nearly agree. Toward the poles, and for a planet close to an angle, they can disagree by a whole house, which is why our comparison tool casts a chart once and shows all thirteen side by side.
Frequently asked
Which house system should I use?
There is no single right answer. Our written interpretations use Placidus throughout so a reading never mixes two systems.
Why do the systems disagree more at high latitudes?
Because the ecliptic's angle to the horizon becomes extreme, so time-based and space-based divisions diverge.