Planetary Domicile (Rulership) in Astrology, Explained
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Domicile (sometimes called rulership) is the sign each of the seven classical planets is said to govern as its own house. It is the foundation dignity that every other dignity in the system is compared against.
The table
The Sun rules Leo and the Moon rules Cancer — one sign each, since they are the two "lights" rather than ordinary planets. The other five planets rule two signs each: Mercury rules Gemini and Virgo, Venus rules Taurus and Libra, Mars rules Aries and Scorpio, Jupiter rules Sagittarius and Pisces, and Saturn rules Capricorn and Aquarius. Together that covers all twelve signs exactly once each — there is no leftover sign and no double-assignment.
Where it comes from
This table is set out in Ptolemy's Tetrabiblos I.18 ("On the Houses of Each Star"), and it is one of the least disputed points in the whole system — later astrologers who disagree on almost everything else still use this same set of twelve. We checked our table against the source text directly and it matches sign for sign.
Why it matters for a reading
A planet sitting in the sign it rules is traditionally read as being "at home" — comfortable, acting more like itself, with fewer complications than when it sits in a sign it has no particular connection to. It's the dignity every other one (exaltation, triplicity, and so on) gets measured against, which is why we always show it first.
What we do and do not add
We calculate which sign each of your planets sits in and whether it matches that planet's domicile, from your actual birth data. We don't treat domicile as a grade on a report card — it's one factor among several dignities, not a verdict on its own.
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