Composite chart: what it shows about a relationship and how to read it

A composite chart is one chart for two people: each planet sits at the midpoint between the same planet in both birth charts. Astrologers read it as a portrait of the relationship itself, the "us" that two people form together, rather than of either person. Where synastry compares two charts side by side, the composite turns them into a third chart with its own Sun, Moon, Venus, Ascendant, houses and aspects.

TL;DR: A composite chart describes what a relationship is like as a whole and what it revolves around; synastry describes how two people affect each other. Numato places every composite planet at the midpoint of the shorter arc between the two positions and builds the Ascendant and houses from the midpoint of the two births' sidereal times, so they need the exact birth time of both people. Read the composite Sun, Moon, Venus and Ascendant first, then the tightest aspects, as in the New York and London example below.

What is a composite chart?

To build a composite chart, you take each pair of matching placements (the two Suns, the two Moons, the two Venuses and so on) and find the point exactly halfway between them. That midpoint becomes the composite Sun, the composite Moon, the composite Venus. The result looks like an ordinary birth chart, with planets in signs, houses and aspects, but it doesn't belong to either person.

Here is one midpoint from the example later in this article. One person has the Sun at Cancer 12°06′, the other at Pisces 9°46′. Counting the short way round the zodiac, from Pisces through Aries and Taurus to Cancer, the halfway point is Taurus 10°56′. The couple's composite Sun is in Taurus, a sign where neither person has their own Sun.

Astrological tradition reads the composite as a description of the relationship as a unit of its own: its character, what the two people do together and what the bond tends to revolve around. That is why astrologers speak about "your relationship" when they read it, not about one partner or the other. The midpoint method was popularized by the astrologer Robert Hand in his 1975 book Planets in Composite. It works for any pair of people: partners, friends, business partners, a parent and an adult child.

How Numato calculates a composite chart

The calculator uses the same engine and the same NASA JPL ephemeris (DE440) as for a birth chart. A composite is built in three steps:

1. Planets and points. The Sun, the Moon, the planets from Mercury to Pluto, Chiron, the North Node and Lilith each go to the midpoint of the shorter arc between the two people's positions.
2. Angles and houses. The calculator doesn't simply average the two Ascendants. It takes the midpoint of the two births' sidereal times (the RAMC, the value that fixes where the MC falls) and calculates the MC, the Ascendant and the house cusps from it for the average latitude of the two birthplaces. This is the approach Robert Hand describes. The houses use the house system from your settings, Placidus by default.
3. Aspects. Aspects between the composite points use the same orbs as a birth chart: for example up to 10° for a square between two planets and up to 5° between a planet and the Ascendant or MC.

Two details follow from the method. A midpoint has no motion of its own, so a composite chart has no retrograde planets: you won't see the ℞ symbol in its planet table. And because every pair is averaged on its own, the shorter-arc rule can occasionally put composite Mercury or Venus on the far side of the wheel from the composite Sun, a placement no real sky shows. It happens when the two people's Suns are almost opposite each other, and it is a known quirk of the midpoint method, not a calculation error.

Composite vs synastry: what's the difference?

Both techniques start from the same two birth charts, but they answer different questions. Synastry keeps the charts separate and looks at how one person's planets land on the other person's chart: whose Venus touches whose Mars, and which houses the other person's planets fall into. The composite merges the two charts into one and describes the relationship from the inside. Our guide to the synastry chart covers the first approach in detail.

The two views complement each other. A couple can have tense contacts in synastry and a calm composite, or the other way round, and that isn't a contradiction: synastry describes how each person experiences the other, while the composite describes what they build together and how the pair comes across to other people. Astrologers often read both.

How to read a composite chart

You read a composite much like a birth chart, with one change of subject: every placement describes the relationship, not a person. Start with four points, then the houses and aspects.

The composite Sun: what the relationship revolves around

In astrology the Sun stands for identity and purpose. In a composite it describes the core of the relationship: what the two people do together and what they feel the relationship is "for". The sign shows the style (a Taurus Sun describes a relationship that builds slowly and steadily, a Gemini Sun one built on conversation and ideas), and the house shows the area of life where the relationship is most visible: the 4th house points to home and family, the 10th to shared goals and public life, the 11th to friends and plans for the future.

The composite Moon: what the pair needs to feel safe

The Moon stands for emotions and needs. In a composite it describes what makes the two people feel safe together: a shared routine, a home base, time with friends or room to talk. Its sign describes the emotional tone of the relationship, and its house shows where the pair looks for comfort. The Moon moves fastest of all the bodies in a chart, so it is also the composite point most sensitive to birth times.

The composite Venus: how affection shows

Venus stands for closeness, pleasure and what a person finds beautiful. In a composite it describes how affection shows up between the two people and what they enjoy doing together. With composite Venus in Taurus, that might be comfort and familiar routines; in Gemini, conversation and trying new places; in Capricorn, care shown through reliability and keeping promises.

The composite Ascendant: how others see you as a pair

The Ascendant stands for first impressions and the way someone approaches the world. In a composite it describes how the relationship comes across to other people and how the pair starts new things together. The planet that rules the Ascendant's sign is the composite chart ruler, and tradition links that theme with the house the ruler sits in; the calculator names it as "Chart ruler" under the planet table. The composite Ascendant exists only when both birth times are exact.

Houses and the composite 7th house

Composite houses work like the houses of a birth chart: a planet's house shows the area of shared life where its theme plays out. The 7th house carries extra weight in a relationship chart, because tradition ties it to partnership and commitment itself. Planets there, especially close to the composite descendant, describe how the two people handle being a pair and the agreements between them. Our guide to the 7th house in astrology explains the house and each sign on its cusp.

Aspects in the composite

Aspects in a composite are the angles between the composite planets, and you read them as in a birth chart: a conjunction merges two themes, a sextile or trine lets them work together easily, a square or opposition creates friction the couple needs to work with, and a quincunx calls for constant fine-tuning. The guide to aspects in astrology describes each one and the orbs. Start with aspects to the Sun, Moon, Venus and the angles, and with the tightest orbs. Aspects between Uranus, Neptune and Pluto change slowly, so for two people of a similar age the composite mostly repeats what both birth charts already share; they say little about this particular relationship.

Example: a composite chart for New York and London

A fictional couple, calculated with the Numato engine (the same one the calculator uses, with its default settings: tropical zodiac, Placidus houses):

• Person A: born in New York on July 4, 1995, at 9:20 a.m. (EDT, UTC−4);
• Person B: born in London on February 28, 1990, at 3:20 p.m. (GMT, UTC+0).

Degrees are shown as in the calculator, in degrees and arcminutes:

Two things are worth noticing in the table. Person A's Moon is in Virgo and Person B's in Aries. The shorter arc between them runs back through Leo, Cancer, Gemini and Taurus, so the composite Moon lands in Cancer, not in Capricorn on the opposite side of the wheel. And the composite Ascendant, Leo 21°12′, lies between the two Leo Ascendants but isn't their simple average (that would be Leo 21°43′), because the calculator derives it from the averaged sidereal time, for an average latitude of about 46.1° N.

For this composite the calculator lists 38 aspects: 19 strong ones (major aspects and quincunxes with an orb up to 3°) straight away and 19 more under "Show weaker aspects (19)". Here are four that involve the Sun, the Moon, Venus and the Ascendant:

Sun in Taurus in the 10th house, conjunct the MC (0°27′). Taurus stands for calm, persistence and comfort; the 10th house for career, goals and how others see you. Tradition reads this as a relationship organized around shared goals and plans, one that other people notice and see as steady. With the composite Sun almost exactly on the MC, the pair tends to be known for what the two build together, whether a home, a business or a long-term plan. The composite Ascendant is in Leo, so the Sun is also the chart ruler: the calculator shows "Chart ruler: Sun", which puts the same theme at the center a second time.

Moon in Cancer in the 11th house, sextile the Sun (0°53′). Cancer is the Moon's own sign and stands for care, home and closeness; the 11th house covers friends, groups and plans for the future. In the tradition, this pair feels safe when the two look after each other and share a circle of friends and plans. The sextile links what the relationship revolves around (the Sun) with what it needs (the Moon). Tradition calls a sextile an opportunity worth taking: it works once the two act on it, for example by keeping room for friends in a busy shared calendar.

Venus in Aries in the 9th house, square the Moon (3°29′). Aries stands for directness and new starts; the 9th house for travel, studies and beliefs. Tradition reads affection in this relationship as showing through spontaneity: a trip booked at short notice, a course taken together. The square describes friction between that impulse and the Cancer Moon's need for safety and a familiar base. Day to day, it can look like a pair that plans adventures on a whim and then needs a quiet week at home. Tradition reads the square as tension that pushes the couple to act, here by finding a rhythm with room for both.

Saturn in Aquarius in the 7th house, opposite the Ascendant (2°12′). An opposition to the Ascendant puts Saturn 2°12′ from the composite descendant, at the start of the 7th house of partnership. Saturn stands for duties, limits and patience; in relationships, tradition links it with commitment and a sense of obligation, sometimes also with coolness or a feeling of being judged. Here it describes a relationship that takes its agreements seriously and needs clear expectations, which talking through openly helps with. The composite 7th house begins in Aquarius 21°12′, and tradition adds the Aquarius need for friendship, equality and independence within that commitment; our 7th house guide describes the 7th house in Aquarius in more detail.

The rest of the list follows the same logic. The first entry, Mercury quincunx Pluto (0°00′), is there because the list is sorted by orb. The Uranus–Neptune conjunction (0°16′) mostly repeats what both birth charts share: both people were born when Uranus and Neptune were in Capricorn. Under "Aspect patterns" the calculator also shows the Moon–Venus square as part of a T-Square with Uranus, with Venus at the apex.

What changes when a birth time is missing

A composite needs the birth times of both people for its angles and houses. If even one of the two times is unknown, approximate or only a time of day, the calculator shows the composite planets in signs only, without the Ascendant, the MC or houses. That rule is stricter than for a single birth chart, where an approximate time can still be enough as long as the Ascendant and MC stay in the same sign throughout the time range. For the composite, even "3:20 p.m., give or take 15 minutes" isn't enough: both times need to be entered with "I know the exact time".

Here is the same couple with Person B's birth time unknown:

• What drops out: the Ascendant, the MC, the houses and the chart ruler. In the couple's Big Three, the Ascendant card says "The couple's Ascendant depends on the exact birth time of both people — we don't calculate it without them." The aspect list shrinks from 38 to 32: the six aspects to the Ascendant and MC disappear, including the Sun–MC conjunction and the Saturn–Ascendant opposition from the example.
• What barely moves: the composite Sun and the planets from Mercury to Pluto. The composite Sun shifts from Taurus 10°56′ to Taurus 10°52′, because these bodies move little in a day.
• What becomes less certain: the composite Moon. For an unknown time, the calculator uses noon local time on that birth date and shows the composite Moon at Cancer 9°02′. Over the whole of February 28, 1990, it could lie anywhere from Cancer 5°23′ to Cancer 12°41′, a spread of about 7°: half the distance Person B's own Moon covers that day. Its aspects change with it. Calculated for noon, the composite Moon loses its opposition to Neptune and gains a sesquiquadrate to Mars; with a London birth at midnight, it would also lose the opposition to Uranus.

In the composite, the calculator doesn't mark which Moon aspects depend on the missing time, so read them with care. When both times are unknown, the calculator uses noon for both people and the composite Moon is at Cancer 9°46′, but it could lie anywhere from Cancer 2°52′ to Cancer 16°41′, a spread of about 14°. In this example it stays in Cancer either way; a composite Moon near the start or end of a sign can change sign.

Even with exact times, the composite angles depend on both clocks. If Person B had been born at noon instead of 3:20 p.m., Person B's own Ascendant would move by about 37° and the composite Ascendant by about 19°, from Leo 21°12′ to Leo 2°27′. Saturn would move from the 7th house into the 8th and the Moon from the 11th into the 12th. That's why a composite reading built on the 7th house or the Ascendant needs two recorded birth times, not "sometime in the afternoon".

What a composite chart can't tell you

We calculate the two birth charts astronomically, from NASA JPL ephemerides, and the composite from them by plain arithmetic. The meanings come from astrological tradition, described in plain language. That tradition has limits:

• It doesn't say whether to start, stay in or end a relationship, or how long it will last. A composite describes the character of a bond, not its future.
• It doesn't score compatibility. No composite placement adds up to a percentage match, and a tense composite isn't a bad relationship: tradition reads squares and oppositions as matters to work on, not verdicts.
• It doesn't describe either person. For that, read each birth chart; for how the two affect each other, read the synastry.
• It isn't a picture of a real sky. The composite planets are calculated midpoints, so the chart doesn't show the sky at any real moment.
• It means the same for every gender and every kind of relationship. A composite Venus in Aries describes the same thing for any couple, friendship or business partnership.

When a relationship is in crisis, a couples therapist or a mediator is the better support.

How to make your own composite chart

1. Open the composite chart calculator and enter both people's birth date, time and place. For the Ascendant and houses, choose "I know the exact time" for both.
2. At the top you'll see each person's moment of birth (date, time, time zone and UTC offset), then "The couple's shared chart" and the couple's Big Three: the composite Sun, Moon and Ascendant with their signs and degrees.
3. Below are the "Composite chart wheel" and four tabs: "Planets" (sign, degree and house of each composite planet, with the chart ruler), "Aspects" (sorted from the tightest orb, with aspect patterns underneath), "Houses" and "Balance".

By default the composite uses Placidus houses, like the birth chart; in the settings you can switch to another house system. To see how the two charts affect each other, run the synastry calculator with the same data: it shows both birth charts on one wheel and lists the aspects between them.

Frequently asked questions

Which is more important, synastry or the composite chart?

Neither replaces the other. Synastry shows how two people affect each other: what draws them together, what irritates them and what each brings out in the other. The composite shows what the relationship is like as a whole and what it revolves around (see the comparison table). Many astrologers read synastry first, then the composite as the portrait of the pair. A tense contact in one and an easy one in the other describe different layers of the same relationship.

What is the most important placement in a composite chart?

Tradition starts with the composite Sun, which describes what the relationship revolves around, and its house, which shows where the relationship is most visible. Next come the Moon (what the pair needs to feel safe), the Ascendant (how the relationship comes across) and Venus (how affection shows). Planets close to the four angles and the tightest aspects to the Sun and Moon add the most detail. In the New York and London example, that is the Sun conjunct the MC at 0°27′.

Can you make a composite chart without birth times?

Yes, in part. Without both exact birth times, the calculator shows the composite planets in signs only, with no Ascendant, MC or houses. The slower planets move little in a day, so their composite signs rarely change. The exception is the composite Moon: for an unknown time the calculator uses noon on that birth date, so the Moon can be several degrees off, within a range of about 7° in our example. More in what changes when a birth time is missing.

Why does another site show a different composite chart?

Usually because of the angles and houses. Some programs take the simple midpoint of the two Ascendants and of each pair of house cusps; Numato derives them from the midpoint of the two sidereal times, as Robert Hand describes (see how Numato calculates a composite chart). In our example, the simple midpoint of the Ascendants would be Leo 21°43′, not Leo 21°12′. A different house system, or a Davison chart presented as a "relationship chart", also changes the result. The composite planets should match.

What is the difference between a composite chart and a Davison chart?

Both describe a relationship with a single chart, but they are built differently. A composite averages the positions of the planets, so it doesn't correspond to any real moment. A Davison chart, named after the astrologer Ronald Davison, takes the moment halfway between the two births and the place halfway between the two birthplaces, and casts an ordinary chart for that moment and place. The Numato calculator makes composite charts, not Davison charts.

Does a composite chart work for friends, family or business partners?

Yes. The method needs only two birth charts, so it can describe any pair: friends, siblings, a parent and an adult child, or co-founders. Tradition reads the same placements in the light of the relationship you're looking at: a composite Sun in the 10th house describes shared goals for business partners just as it does for a couple. The calculator works the same way for every pair, so enter the two people's data and read the result as a description of that particular relationship.

This content is for educational purposes and supports self-reflection; it does not replace professional advice.