Free House System Comparison Calculator
House systems change which house a planet falls in, not its sign, so the question "which house system should I use" only matters if your placements actually move between them. This calculator runs your chart through Placidus, Whole Sign, Koch and Equal houses at once and shows you, planet by planet, where they agree and where they don't.How it works ↓
Calculating your placements…
House systems divide your birth chart into twelve houses by different mathematical methods, so the same planet can land in a different house depending on which system is used. This calculator casts your chart in Placidus, Whole Sign, Koch and Equal houses side by side, so you can see exactly which of your placements shift and which stay put.
What a house system actually changes
Your planets' signs and degrees come from a single fact: where the planets physically were at the moment you were born. No house system touches that. What a house system decides is which of your twelve life areas, houses, each of those fixed positions falls into.
Think of the signs and degrees as the furniture and the house system as where the walls of the room go. Move the walls and a couch that was in the living room can end up in the hallway, but it is still the same couch. That is what happens when a planet changes house between systems: nothing about the planet moved, only the boundary around it did.
Why the systems disagree
Placidus divides the sky by time: it splits the arc each degree takes to rise into equal segments, which is why its houses can stretch and compress unevenly depending on your latitude. Whole Sign, the oldest system still in common use, skips that math entirely and makes each house exactly one zodiac sign, starting with the sign your Ascendant falls in.
Koch also uses time-based arcs, similar in spirit to Placidus but built from a different starting curve, so the two often agree closely but not always. Equal House sidesteps the whole time-arc problem by cutting the chart into twelve even 30-degree slices from the Ascendant. Four different starting assumptions, run on the same birth data, and four different sets of cusps come out.
How to read your comparison
Look at the "where they disagree" table first: it already did the work of filtering out everything that matches. Every planet listed there changed house in at least one of the four systems for your chart; every planet missing from it landed in the same house across all four.
Disagreements cluster around planets that sit close to a house cusp in any one system. A planet solidly in the middle of a house rarely moves no matter which system you pick, because all four systems would have to disagree about where an entire third of the sky begins, which they mostly don't. It is the borderline placements, not the central ones, that are actually sensitive to your choice.
When house system choice matters most
The higher your birth latitude, the more the systems can pull apart. Near the poles, Placidus and Koch can produce very uneven houses or fail to calculate at all, which is part of why Equal House and Whole Sign exist as simpler alternatives that never break down.
Birth time also matters more here than almost anywhere else in astrology. House cusps are derived entirely from the exact moment you were born, so an estimated birth time can move a placement across a house boundary in every system at once, not just one. If your birth time is uncertain, treat any single close comparison result with the same caution you would treat one house placement.
Which system to actually use
There is no version of this question with a single correct answer, and any calculator that tells you otherwise is overstating what the field agrees on. Placidus is the default in most modern software and the most widely taught system in contemporary Western astrology. Whole Sign is the system the earliest Hellenistic astrologers used and has returned to wide practice through the traditional astrology revival.
A common working approach is to pick the system your tradition or teacher uses and stay consistent with it, rather than switching systems to chase a more flattering house placement. Where this calculator earns its keep is showing you, honestly, how much is actually at stake in that choice for your specific chart.
Comparing systems vs. picking one
This page is for the comparison itself: seeing your chart across four systems at once so you can judge how sensitive your own placements are to the choice. If you already know which system you want to read from day to day, a single-system chart is a cleaner tool for that than a four-way grid.
Whole Sign, Koch and Equal each have their own dedicated calculator, linked below, that casts your full chart in just that one system.
Frequently Asked Questions
Which house system should I use?
There is no single correct answer, and different traditions favor different systems. Placidus is the modern software default; Whole Sign is the oldest system still in wide use. Comparing them side by side, as this calculator does, shows you how much your own placements actually shift before you decide it matters.
Why did none of my planets change houses?
That is a real result, not a broken one. House systems only disagree near cusp boundaries, and most charts have several planets sitting well inside a house rather than close to its edge. If nothing moved for you, house system choice genuinely will not change how your chart reads.
Is Placidus the most accurate house system?
Accuracy is not really the right frame here. Every house system takes the same exact birth data and applies a different mathematical rule for dividing it into twelve houses, so none of them is measuring something the others get wrong. Placidus is simply the most common default today, not a more correct calculation.