Essential
Dignities

Every sign has rulers at five levels, and a planet's essential dignity is the rulership it holds in the place where it stands. Mars at 3° Scorpio is in its own sign, rules the water signs by night and owns both the term and the face that cover 3°. Mars at 3° Libra holds none of those and sits in the sign opposite its own.

The levels, from strongest to weakest, are domicile (the sign the planet rules), exaltation, triplicity (rulership of the sign's element), term (a span of a few degrees) and face (a 10° third of the sign). The two debilities are detriment, the sign opposite a domicile, and fall, the sign opposite an exaltation. Ptolemy set out the houses, the triangles with their day and night rulers, the exaltations and the terms in Book I of the Tetrabiblos in the second century. Dorotheus of Sidon gives each triangle a third, participating ruler, and the faces in the Chaldean order come down through later tables. William Lilly's Christian Astrology (1647) printed the scheme as one table and, in a separate table of fortitudes and debilities, gave each level a point value; those values are the ones this calculator adds up.

“Essential” separates these rulerships from accidental dignity, which is about a planet's situation in the chart: its house, its speed and direction, its distance from the Sun. The calculator scores essential dignity only. A planet with a low score can still be angular, fast and well aspected, and Lilly scored those conditions in a separate column.

The table below is generated from the same constants the calculator scores with. Each row is a sign: the planet that rules it, the planet exalted in it (with the degree later tables single out), the planets in detriment and in fall there, and the three triplicity rulers of its element.

Read a row across: in Aries, Mars rules, the Sun is exalted, Venus is in detriment and Saturn in fall, and by day the Sun rules the fire signs, by night Jupiter, with Saturn participating in both. Gemini, Leo, Scorpio, Sagittarius and Aquarius host no traditional exaltation. The calculator counts an exaltation anywhere in its sign; the degree column is for reference.

The terms

Each sign is split into five unequal spans, one for each planet other than the Sun and Moon. The calculator uses the Egyptian terms, the version Ptolemy describes as the most generally accepted in his day. A span ends where the next begins: a planet at exactly 6°00′ Aries is in Venus's term, not Jupiter's.

Added up across the zodiac, Venus holds 82°, Jupiter holds 79°, Mercury holds 76°, Mars holds 66° and Saturn holds 57°. The Egyptians matched these totals to the years of life each planet allots. Ptolemy objects that the sums prove nothing, since many different tables would add up the same way, and that the order of rulers within the signs follows no consistent rule. The table he preferred is discussed in the section on Lilly below.

The faces

The faces divide each sign into thirds, 36 in all. They follow the Chaldean order of the planets, slowest to fastest (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), starting from Mars at 0° Aries and going round again: Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars and so on. Because 36 is one more than five rounds of seven, the sequence ends where it began, and Mars rules 6 faces to everyone else's 5.

Modern rulerships (not scored)

Uranus, Neptune and Pluto were found in 1781, 1846 and 1930, long after the scheme was fixed. The rows below are modern proposals: the domiciles are widely used, while the exaltations shown are one of several sets in circulation. They are listed so you can see what other software may show; they never enter a score here.

Your date, time and place of birth go to our API, which computes tropical, geocentric positions with its ephemeris (the details are on the methodology page). The API also reports the chart's sect: a day chart when the Sun is above the horizon, which it tests by asking whether the Sun lies 180° to 360° ahead of the true Ascendant in zodiacal order. The sect calculator explains that test. Houses play no part in the score.

Then, for each of the seven traditional planets, the code in computePlanetDignity checks:

1. Domicile and detriment by sign, from the ruler table.
2. Exaltation and fall by sign, anywhere in it.
3. Triplicity: the element of the sign gives three rulers. The planet scores if it is the day ruler in a day chart, the night ruler in a night chart, or the participating ruler in either.
4. Term: the span of the Egyptian table that contains the planet's degree.
5. Face: the 10° third that contains it.

The points are added with no cap and no weighting, so a planet in its fall that also holds triplicity, term and face can end up positive. The label beside each total comes straight from the score: +8 or more is “strongly dignified”, +3 to +7 “dignified”, +1 or +2 “slightly dignified”, −1 to −4 “debilitated” and −5 or lower “severely debilitated”. A planet with no dignity and no debility is labeled peregrine and scores 0; a 0 reached by a dignity cancelling a debility is shown as “net 0”.

Positions are printed cut to the minute of arc, not rounded, so 5°59.7′ shows as 5°59′, as it does across this site. Uranus, Neptune and Pluto are left out of the score.

Scoring every half degree of the zodiac in both sects with the calculator's own code gives each planet's range. Mercury and Mars share the top score of +11, and only Mercury can reach −9, by being in detriment and fall in the same sign. The Sun tops out at +8: it holds no terms anywhere, so its best placements stack domicile or exaltation with triplicity and, at most, a face.

The table also shows where sect matters. Several maximums exist only by day or only by night, because they depend on a triplicity rulership; a participating ruler takes its points in either sect, which is why the Moon in Cancer and Mars in Capricorn score the same whatever the time of birth.

Prince William was born at 9:03 PM (UTC+1:00) on June 21, 1982, in London, the time given in the official birth announcement. Our API puts the Ascendant at 27°28′ Sagittarius and the Sun at 0°06′ Cancer, 2°37′ of the zodiac past the Descendant (27°28′ Gemini): above the western horizon, so this is a day chart. The scores below are recomputed with the calculator's code when this page is built and checked against an independent calculation in the generating script.

How three of the totals are built:

• Saturn at 15°30′ Libra: exaltation +4 (Saturn is exalted in Libra), triplicity +3 (Saturn rules the air signs by day), face +1 (10°–20° Libra is Saturn's face): +8.
• Moon at 4°57′ Cancer: domicile +5 (Moon rules Cancer), triplicity +3 (Moon is the participating ruler of the water signs, counted by day and by night): +8.
• Mars at 9°12′ Libra: detriment −5 (Libra is opposite Mars's own sign): −5. Mars holds no triplicity in Libra (the air rulers are Saturn, Mercury and Jupiter), and its degree falls in Mercury's term and the Moon's face, so nothing offsets the detriment.

The Moon, Venus, Saturn and Mercury score above zero. The Sun and Jupiter hold no dignity and no debility and score 0. Mars is the one planet below zero.

Sect matters here because the birth came close to sunset. The chart would have turned to night at 9:14 PM, 12 minutes after the recorded birth time. Scored as a night chart, the same positions give Mercury +8 instead of +5, Venus +5 instead of +8 and Saturn +5 instead of +8, for a total of +21. The Moon keeps its triplicity either way, as the participating ruler of the water signs. An error of 12 minutes in the recorded time would be enough to change this chart's scores, which is why the form asks for the time.

The point values are Lilly's, but three of the tables underneath them are not, and his table of fortitudes and debilities also credits mutual reception. The calculator stays with the Dorothean triplicities and the Egyptian terms. Here is what changes under Christian Astrology:

Triplicity. Lilly lists two rulers per element, one by day and one by night, and gives the water signs to Mars at both times. Dorotheus, whose scheme the calculator follows, names a third, participating ruler for each element, and the calculator gives it the full +3 in either sect. The water row differs most: by day Venus rules there for Dorotheus and Mars for Lilly. Ptolemy's own account in Tetrabiblos I.18 puts Mars over the water signs with Venus by day and the Moon by night.

Terms. Lilly's table follows the terms Ptolemy gives in Tetrabiblos I.21, which he says he took from a damaged ancient manuscript that ordered the rulers more consistently than the Egyptian table. In Aries the two tables agree on the first span and on the order of rulers but move every later boundary, so Venus, Mercury, Mars and Saturn cover different degrees. The surviving copies of Ptolemy's table disagree with each other on a few boundaries in other signs, so this page shows only Aries rather than a second full table it can't vouch for.

Peregrine. For Lilly a planet is peregrine whenever it has none of the five dignities, and his table charges it −5, the same as detriment. The calculator scores such a planet 0 and keeps the word for planets with no debility either.

What would change for Prince William

• Triplicity: The Moon (4°57′ Cancer) loses its 3 triplicity points, because Lilly's day ruler of the water signs is Mars.
• Peregrine: The Sun and Jupiter would each be charged −5 instead of 0. Mars, in detriment with no dignity, is peregrine by Lilly's definition as well; his table doesn't say whether the two charges add up, so this page doesn't add them.
• Mutual reception: none in this chart, by sign or by exaltation, so nothing changes.
• Terms: none of Prince William's planets is in its own Egyptian term, and none is in its own term in Ptolemy's table as Robbins prints it either, so the changes above do not depend on which term table is used.

• Ptolemy, Tetrabiblos, Book I, translated by F. E. Robbins (Loeb Classical Library, 1940): chapter 17 on the houses (domiciles), 18 on the triangles, 19 on exaltations, 20 with the Egyptian terms and 21 with Ptolemy's own terms. The Egyptian table here matches chapter 20 sign by sign.
• Dorotheus of Sidon, Carmen Astrologicum, Book I, translated from the Arabic by David Pingree (1976): the triplicity lords by day and by night, with a third partner lord for each triangle.
• William Lilly, Christian Astrology (London, 1647): the table of essential dignities (Book I, p. 104) and the table of fortitudes and debilities with its point values (p. 115).

The worked example uses Prince William's official birth announcement; positions come from our API, and the generating script scores them with a separate implementation of these rules before the page recomputes them.