In the sextile, it is 60 degrees: a sixth of the wheel. The two planets fall in elements that go together, fire with air, earth with water, which is the same combination as the opposition, only a sixth apart instead of half a turn.

An aspect is the distance between two planets measured on the wheel of the zodiac. When that distance falls close to an angle the tradition recognises, the two are said to form an aspect, and that is what links one part of the chart to another. The whole logic is in what an aspect is.

I measured 200,000 charts drawn at random between 1930 and 2025, with the same orbs this site uses to cast charts and with the engine’s own rule: each pair of planets forms one one aspect, the tightest one.

The square (90°) appears 2.90 times per chart on average, is in 93.5% of charts and accounts for 23.4% of the five major aspects; the sextile (60°), 2.82 times, in 94.1% of charts and with 22.8%; the trine (120°), 2.68 times, in 92.9% and with 21.6%; the conjunction (0°), 2.47 times, in 93.9% and with 19.9%; the opposition (180°), 1.52 times, in 73.0% and with 12.3%; and the quincunx (150°), which stays out of the count of the five major ones, 0.93 times, in 58.2% of charts.

The sextile is in second among the five, with 22.8%, and at the same time it is the one that shows up in more charts: 94.1%, more than any other. It is no contradiction, the sextile has the tightest orb of the five major aspects (six degrees with the Sun or the Moon, against eight for the square and ten for the conjunction), so it forms less often per pair and still reaches almost everyone, because 60 degrees are two places on the wheel.

And there is a number this measurement shows that almost no astrology text says out loud: 94.1% of charts have at least one sextile. Having one distinguishes almost nobody. What distinguishes is WHICH planets it links, and which houses they are in.

The sextile opens the door and pushes nobody. It is the aspect of opportunity, and opportunity is something you can miss: it describes an ease that only exists if the person takes the step. Unlike the trine, which delivers, the sextile offers, and whoever does not accept spends a life without knowing they had it.

The limit is worth saying: these are tendencies, not a verdict. An aspect describes how two functions of the chart talk to each other, it does not foretell events, diagnoses nobody and decides nothing for you.

The aspect on its own says almost nothing: what gives it a subject are the two planets. These four pairs are among the most common, and they show how the same geometry changes face:

• Sun–Moon: identity and need help each other when the person lets them, and this doesn't happen on its own.
• Mercury–Mars: thinking and acting join up well, and the join has to be made on purpose.
• Venus–Saturn: affection gains structure when there is a choice, and without a choice it becomes mere caution.
• Moon–Neptune: sensitivity has access to the imagination, which sits idle if nobody uses it.

Notice that the angle is the same in all four and the subject is completely different. That is why "I have a sextile" is not a reading, it is the start of one.

Only two pairs never form a sextile, and it is the shortest list of any aspect. Mercury does not get 27.8° from the Sun and Venus does not pass 47.2°: neither of them reaches 60 degrees. Mercury and Venus between themselves reach 73.8°, so those two do form it, and Neptune with Pluto, which have formed nothing else for a century, form exactly this one: they spent a hundred years between 42.6° and 65.3°, and the sextile is the only aspect in that band.

This is not a rule of one school: it is the orbits of the planets. And it is a useful check at home, if a site shows one of those pairs with this aspect, it is not calculating the sky.

Two planets almost never fall on the exact angle. The orb is the leeway allowed: how far off the angle the aspect can be and still count. And it does not belong to the aspect alone, it depends on who forms it.

This site uses a wider orb for the Sun and the Moon, a narrower one for the outer planets, and takes the average of the two. Measured across the same 200,000 charts: when a sextile happens, the average distance to the exact angle is 2.30°. That is, the tight aspect is far more common than the one on the edge, and your chart shows the exact distance of each, instead of only the name.

The question that matters is not how many you have: it is where they fall. An aspect between two planets in the 10th house speaks of work and reputation; the same aspect between the same planets in the 4th speaks of home and family. The house depends on the hour and city of birth, and it is what turns geometry into a reading.

The two texts that carry on from here are what an astrological house is, which explains the twelve areas, and what the birth chart is, which puts the whole picture together.

And the questions that come up most on this subject, with the short answer: