Lesson 20 of 27 · Intermediate
House Systems in Astrology: Whole Sign vs Placidus vs KP
Why the same birth details can land a planet in a different house, depending on the software.
The short answer
A house system is the rule that divides the sky into twelve houses around a chart. Whole sign, which Astra uses, makes each house exactly one sign, from the rising sign onward. Bhava chalit, Placidus, and KP instead measure boundaries from the ascendant and midheaven's exact degrees, which can shift a planet into a neighbouring house.
What a house system actually decides
Every birth chart agrees on the twelve houses themselves — the 1st is self, the 7th is partnership, the 10th is career, and so on. What house systems disagree about is narrower and more mechanical: exactly where the boundary between one house and the next falls. Move that boundary by a few degrees and a planet sitting near it can be read as belonging to a different house entirely.
Every system starts from the same point: the ascendant, or lagna — the degree of the zodiac rising on the eastern horizon at the moment of birth. From there, the systems part ways over how to step around the rest of the circle.
Ascendant (Lagna)the point of the zodiac rising on the horizon at the exact moment and place of birth; the anchor every house system starts counting from
Whole sign houses — the oldest method, and the one Astra uses
Whole sign is the plainest of the house systems and the one classical Vedic literature assumes throughout. The sign the ascendant falls in becomes the entire 1st house. The next sign along becomes the entire 2nd house. And so on, all the way around — twelve signs, twelve houses, one each. Every house is a clean 30°, and there is no cusp arithmetic to compute at all.
Whole sign housesa house system in which each house is exactly one full sign, counted in order from the sign the ascendant occupies
Because a house and a sign share the same edges, a graha's house in a whole-sign chart never depends on fine-grained math — only on which sign it occupies. That is also why sign-based techniques like house lordship, drishti, and yogas are all defined the way they are: they were built on a sign-equals-house foundation from the start.
Bhava chalit — the cusp chart consulted alongside it
Indian practice keeps a second chart for a narrower purpose. Instead of starting from the whole sign, the bhava chalit measures house boundaries from the exact degrees of the ascendant and the midheaven — the point overhead at birth — and works the rest of the cusps out from those two angles. The houses it produces are not clean 30° wedges; a house can run wider or narrower depending on the birth time and latitude.
Bhava chalita cusp-based house chart, worked out from the exact degrees of the ascendant and midheaven, that is read alongside the whole-sign chart rather than instead of it
Traditionally the rashi (whole-sign) chart keeps the final word on which sign a graha occupies, who rules which house, and which yogas are present. The chalit is consulted separately, mainly to judge how strongly a house is expressing itself when a graha sits close to one of its edges. Astra's own bhava chalit works out its cusps using the same semi-arc mathematics that Placidus and KP use below — it is a genuinely different calculation from the whole-sign chart, not a relabelling of it.
Placidus and KP — houses measured by time, not by sign
Western astrology mostly uses Placidus, and the Indian school called KP (Krishnamurti Paddhati) uses Placidus cusps too, so it is worth understanding on its own. Placidus divides the sky by time: it asks how long each degree of the ecliptic takes to rise from the horizon up to the midheaven, and slices the twelve houses so that span is divided evenly. The result is houses of noticeably unequal width, especially far from the equator, where some houses can be twice the size of others.
KP layers a further refinement called sub-lords on top of the same Placidus cusps, used mainly for very specific-question predictions rather than for reading a whole life. Both systems share the same limitation: the arithmetic depends on how fast the ecliptic degrees are rising at that latitude, and beyond roughly 66° latitude — inside the Arctic and Antarctic circles — that arithmetic simply breaks down. A chart cast for someone born there cannot be built with Placidus or KP houses at all.
Why the same chart can look different across two apps
Picture an ascendant at 25° Aries. In a whole-sign chart, the entire span from 0° to 30° Aries is the 1st house, so a planet at 27° Pisces sits just behind it, comfortably inside the 12th house. In a Placidus or KP chart for the same birth, the 12th house cusp is measured independently from the midheaven and can fall past 27° Pisces — pulling that same planet into what that system calls the 11th house instead. The planet has not moved; the ruler measuring its house has changed shape.
This is also why comparing house placements across two pieces of software is only fair when they are using the same house system. A graha reported in different houses by two apps is not evidence that one of them made an error — it usually just means they answered the question “which house is this in” with two different rulebooks.
Which house system does Astra use, and why
- It is the system the classical Vedic literature assumes throughout — house lordship, yogas, and drishti are all defined sign by sign
- It never breaks: every birthplace on Earth, including near the poles, gets the same twelve clean houses
- It is fully inspectable — you can verify any house yourself just by counting signs from the ascendant, with no cusp table required
None of this makes Placidus, KP, or bhava chalit wrong. Each has serious practitioners who can point to charts their method reads clearly. They are different instruments built for different jobs, and the honest position is not to declare one universally correct but to be clear about which one a given chart, or a given piece of software, is using.
How to tell which house system a chart was cast with, at a glance
- Check whether every house spans exactly one full sign, edge to edge
- If it does, you are looking at a whole-sign chart — the system Astra's rashi chart uses
- If one sign is split across two houses, or one house contains parts of two signs, the chart was cast with a cusp system — bhava chalit, Placidus, or KP
- To tell those three apart, compare the ascendant degree: if it matches the 1st house cusp exactly and the chart is Vedic, it is most likely a bhava chalit or KP layout rather than a Western Placidus one
Questions people ask
What house system does Vedic astrology traditionally use?
Classical Vedic astrology is built on whole-sign houses, where the ascendant's sign becomes the entire 1st house and the rest follow in order, one sign per house. Lordship, yogas, and drishti are all defined on this sign-by-sign basis. Bhava chalit, a cusp-based chart, is consulted alongside it, but the whole-sign rashi chart keeps the final word.
Why do two astrology apps show my planet in different houses?
They are almost certainly using different house systems. Whole-sign houses match houses to signs exactly, while bhava chalit, Placidus, and KP measure house boundaries from the exact degrees of the ascendant and midheaven instead. A planet sitting near a boundary can fall on either side depending on which method drew that boundary.
What is a bhava chalit chart?
It is a cusp-based house chart used alongside the whole-sign rashi chart in Indian practice, with boundaries measured from the exact degrees of the ascendant and midheaven rather than from whole signs. It is traditionally consulted to judge how strongly a house is expressing itself, while the rashi chart keeps the final say on signs, lords, and yogas.
Is Placidus or whole sign the more accurate house system?
Neither is more astronomically correct; they answer different questions with different conventions. Whole sign ties houses to signs and never breaks anywhere on Earth. Placidus divides houses by time and produces unequal widths, and fails outright beyond about 66° latitude. Classical Vedic technique was built around whole sign, which is why Astra uses it.
Can a house system fail for someone born near the North or South Pole?
Yes, if that system is time-based. Placidus and KP measure houses using how fast ecliptic degrees rise at a given latitude, and beyond roughly 66° latitude that calculation has no solution. Whole-sign houses have no such limit, since they only depend on which sign the ascendant occupies, not on rising times.
What is KP astrology?
KP, or Krishnamurti Paddhati, is an Indian sidereal school that uses Placidus house cusps as its foundation, then adds a further layer called sub-lords for answering narrow, specific questions. It shares Placidus's unequal house widths and its breakdown near the poles, but applies them within a Vedic, sidereal framework.
Which house system does Astra use?
Astra's main chart is whole sign: the ascendant's sign is the whole 1st house, and the rest follow one sign per house. Astra also computes a bhava chalit chart, using the same cusp mathematics as Placidus and KP, for readers who want to check how strongly a house is expressing itself near a boundary.