Compare House Systems
Where your planets fall in all 13 house systems, side by side.
Which house system should you use, and how much does the choice change a chart? The houses are the twelve life areas of a chart, and the systems differ in how they divide the sky between the Ascendant and the Midheaven. Near the equator they nearly agree. Toward the poles, and for planets close to an angle, they can disagree by a whole house.
This tool casts your chart once and shows where every planet falls in all thirteen systems at the same time. Every cell that differs from Placidus is highlighted, so you can see at a glance which planets are house sensitive in your chart. The calculation uses Swiss Ephemeris.
The thirteen systems, in three families
Every system starts from the same two points, the Ascendant and the Midheaven. What separates them is one question: how do you divide the sky in between?
Systems that divide time
These split the hours a degree needs to climb from the horizon to the meridian. They follow the Sun's daily motion, so their houses stretch as you move away from the equator.
Placidus
Splits each degree's climb from horizon to meridian into three equal spans of time. The modern default, and the one most software prints. Its houses distort badly above the Arctic Circle.
Koch
Divides the same climb, but recomputes it for the birthplace's latitude at every cusp. Widely used in central Europe and unusable in the far north.
Alcabitius
Divides the time the Ascendant needs to reach the Midheaven. The standard of medieval Arabic and Byzantine astrology, still used for classical natal work.
Topocentric
Reaches almost the same cusps as Placidus from a different geometry, built around the observer's own place on the globe. Argentine, twentieth century.
Systems that divide space
These divide the sky by measure rather than by time. Most cut one great circle into equal arcs and project the cuts onto the zodiac; Porphyry divides the zodiac arc between the Ascendant and the Midheaven directly.
Regiomontanus
Cuts the celestial equator into twelve equal arcs. The house system of classical horary, where a question is judged by the house its answer falls in.
Campanus
Cuts the prime vertical, the circle running east to west directly over your head. The oldest space based system, from the thirteenth century.
Meridian
Cuts the celestial equator starting from the Midheaven rather than the Ascendant. Latitude does not affect it, so it holds anywhere on Earth.
Horizon
Cuts the horizon circle itself, so the houses line up with compass directions. Also called the azimuthal system.
Porphyry
Trisects the arc between the Ascendant and the Midheaven. The simplest quadrant system, and the ancestor of most of the others.
Systems of equal measure
These give every house the same width and take a single point as the anchor. Nothing stretches, and they hold at any latitude.
Whole Sign
The entire sign holding the Ascendant is the first house, the next sign the second, and so on. The oldest system there is, and it never breaks at any latitude.
Equal
Every house is exactly thirty degrees, counted from the Ascendant. The Midheaven is free to land in the ninth, tenth or eleventh.
Equal MC
The same thirty degree measure, counted from the Midheaven instead. Choose it when the tenth house cusp has to be exact.
Vehlow
Equal houses again, shifted so the Ascendant sits in the middle of the first house rather than at its start.
Frequently Asked Questions
Which house system is best?
There is no single right answer; it is a long standing debate. Whole Sign is the oldest and the Hellenistic standard, Placidus the modern default. This tool lets you see your own chart in all of them and decide, rather than arguing in the abstract.
Why do house systems disagree?
They divide the space between the Ascendant and the Midheaven differently. The angles, the Ascendant and Midheaven, are the same in every system, but the intermediate cusps move, so a planet near a cusp can sit in different houses depending on the method.
Does the house system change my Sun sign?
No. House systems only affect which house a planet falls in, not its sign. Your Sun, Moon and rising signs are the same in every system.