House Systems: Whole Sign vs Placidus

Why there is more than one

Because dividing a sphere into twelve has several defensible answers. You can divide the ecliptic, the celestial equator, or the time it takes a degree to rise. Each choice gives a different set of house boundaries and each has been standard somewhere.

This is a genuine open problem rather than a detail. Two reputable astrologers using different systems will put your Sun in different houses and both will defend it.

Whole sign

The oldest system, used throughout Hellenistic astrology and most of the medieval tradition, and revived in the last thirty years. Your rising sign becomes the entire 1st house, the next sign the entire 2nd, and so on. Every house is exactly thirty degrees.

The advantages are that it is simple, it works at any latitude, and all the old techniques were built on it. This site uses it for that reason: profections, for instance, makes no sense in a system where houses are unequal.

Placidus

The modern default, found in most software and most apps. It divides by the time it takes a degree to rise from the horizon to the midheaven, which produces houses of very unequal size. The midheaven is always the cusp of the 10th, which many astrologers consider the decisive advantage.

It breaks down at high latitudes. Above about 66 degrees north or south some houses become impossible to calculate, which is a real limitation for anybody born in northern Scandinavia or Alaska.

What to do about the disagreement

Run your chart in both. If a planet falls in the same house either way, it is settled. If it moves, you have learned which parts of your reading are system-dependent, which is worth knowing before you build anything on them.

The honest position is that this is unresolved. Anybody telling you their system is correct is expressing a preference, and the preference is usually whichever one they learned first.

How much a system change actually moves

For a chart at a middle latitude, whole sign and Placidus usually agree about more than half the planets and disagree about the rest, mostly by one house. A planet at 28 degrees of a sign is the one most likely to move, because it sits near the edge in any system.

At high latitudes the difference becomes dramatic: Placidus houses can stretch to sixty degrees or collapse to ten, so a chart from Reykjavik can look completely unlike its whole sign version. That is not a reason to reject either, but it is a reason to know which you are looking at.

What people get wrong about this

• Assuming your app's default is the only option. Most default to Placidus without saying so.
• Switching systems until a placement reads the way you want. That is choosing a conclusion and working backwards.
• Using Placidus for a birth near the Arctic or Antarctic circles, where it cannot be calculated properly.
• Believing the question is settled. It is not, and anybody who says otherwise is stating a preference.

Where to read next

the four angles, then how to read a birth chart, then your chart ruler.

If you want this done on your own chart

Everything on this page is general by necessity. A reading built from your own date, time and place is the version that names your placements rather than describing the categories they fall into. If you do not know your birth time, this covers how to find it.