A composite chart is a single chart made from two people's birth charts by taking the midpoint between each matching pair of planets: the midpoint of both Suns becomes the composite Sun, the midpoint of both Moons the composite Moon, and so on. Astrologers read the result as a chart of the relationship itself, as if the couple were a third entity with its own character, purpose and habits.
That makes it a different tool from synastry, which compares two charts side by side to see how each person affects the other. Synastry asks "how do we get along?" A composite asks "what is this relationship like, and what is it for?" Here's how the chart is built, the main alternative, and an order for reading one.
What a composite chart shows
Think of a long-married couple who are, separately, quiet homebodies, yet together host every holiday and know everyone on the street. Or two outgoing friends who, in each other's company, mostly sit on the sofa and talk until two in the morning. Relationships often have a personality that neither person has alone. The composite chart is astrology's attempt to describe that personality.
Because it describes the bond rather than either person, a composite is read with a slightly different vocabulary. The composite Sun is the relationship's core purpose. The composite Moon is its emotional climate: how it feels to be in it on an ordinary Tuesday. The houses show which areas of life the relationship naturally gravitates toward. The technique works for any pair of people, including friends, business partners, and parents and children, not only couples.
If you haven't read about synastry yet, our explainer on what synastry is is the best companion to this one. Many astrologers use the two together.
How the midpoints are worked out
Every position in the zodiac can be written as a number from 0 to 360, counting from 0 degrees Aries. Each sign is 30 degrees, so Taurus begins at 30, Gemini at 60, and so on around to Pisces at 330.
A simple example. One person's Sun is at 10 degrees Aries, which is 10. The other's is at 20 degrees Gemini, which is 80. The midpoint is 45, which is 15 degrees Taurus. That's the composite Sun.
The tricky case. Because the zodiac is a circle, every pair of points has two midpoints, one on each side. Composite charts use the nearer one, on the shorter arc. Suppose one Sun is at 20 degrees Pisces (350) and the other at 10 degrees Gemini (70). A plain average gives 210, which is 0 degrees Scorpio. But the short way between them runs through 0 degrees Aries, and the halfway point on that arc is 30, or 0 degrees Taurus. The composite Sun goes there, not in Scorpio.
Chart software does all of this automatically, but knowing the rule explains results that look strange at first. The Ascendant and house cusps are handled in one of two ways: some programs take the midpoint of the two Ascendants, while others take the midpoint of the two Midheavens and calculate an Ascendant from it for the couple's location. The two methods can give different rising signs, so it's worth knowing which yours uses.
Composite or Davison: two ways to make a relationship chart
The midpoint composite became widely used in the 1970s. A second method, named after the British astrologer Ronald Davison, takes a different route: it finds the midpoint in time between the two births and the midpoint in space between the two birthplaces, and casts an ordinary chart for that moment and location.
The practical difference is that a Davison chart is a real sky. Every planet sits somewhere it actually was on a real day, so the chart never contains impossible combinations. A midpoint composite is a mathematical blend, which occasionally produces placements no real sky could. Many astrologers look at both and find they usually tell a similar story in different words.
Reading a composite in five steps
- Start with the composite Sun, by sign and house. This is the relationship's center of gravity. A composite Sun in Capricorn suggests a bond built around shared goals and long-term plans; in Gemini, one built around conversation, curiosity and variety.
- Then the composite Moon. This describes the emotional atmosphere. A Moon in Taurus feels steady and comfortable; a Moon in Aries feels lively, quick to flare and quick to recover.
- Look at the Ascendant, if you have both birth times. It describes how the relationship comes across to others, and how the two of you tend to start things together.
- Read Venus and Mars. Composite Venus shows how the relationship expresses affection and pleasure; composite Mars shows its drive and how it handles conflict. For the Venus and Mars contacts between the two original charts, see Venus and Mars aspects in synastry.
- Check Saturn and the tightest aspects. Composite Saturn describes the relationship's duties and staying power, and any tight aspect to the Sun or Moon is usually a major theme.
As with any chart, look for repetition. Three factors pointing toward home and family matter more than one.
Where the relationship lives: composite houses
The houses in a composite describe which parts of life the relationship naturally fills. A few common examples, by the house the composite Sun falls in:
- Fourth house: a home-centered bond, often about family, roots and building a private life together.
- Fifth house: romance, play, creativity and fun; the relationship stays young.
- Seventh house: partnership is the point. These couples often feel most themselves as a pair. Our guide to the seventh house explains why it's tied to commitment.
- Ninth house: travel, learning, shared beliefs, a relationship that widens both people's world.
- Tenth house: a visible, public couple, or partners who work together and build something.
- Twelfth house: a private relationship that may feel like a refuge from the world, and sometimes one that's kept out of view.
Houses need accurate birth times for both people. If you're new to them, our introduction to the twelve houses in astrology covers what each one means.
Odd results and how to read them
Because a composite is calculated rather than observed, a few quirks turn up.
- Planets far from the Sun. In a real chart, Mercury and Venus always sit fairly close to the Sun. In a composite, the near-midpoint rule can occasionally put composite Venus or Mercury far from the composite Sun, even roughly opposite it. Astrologers usually read such placements as they appear, while treating them with a little caution.
- A crowded house. Two charts with similar planets can produce a composite with a big cluster in one house. That's read as a strong theme, not a problem.
- The Moon without times. The Moon moves about 13 degrees a day, so without birth times the composite Moon can be off by several degrees, occasionally into another sign.
A composite also isn't a forecast. It describes the shape of a bond; it doesn't say how long the bond will last or whether two people will treat each other well. Those things are still decided by the two people in it.
Getting your own composite
You'll need both people's birth dates, and ideally their times and places. Draw up a free birth chart for each of you first to check the details. If you'd like the combined chart calculated and interpreted in full, the composite chart report does exactly that.
Questions readers ask
What is the difference between synastry and a composite chart?
Synastry compares two separate charts to see how each person's planets affect the other's. A composite merges them into one chart describing the relationship itself. Synastry is about the chemistry between two people; the composite is about the bond they make together.
Can you do a composite chart without birth times?
Partly. You can calculate the composite planets by sign, though the composite Moon may be a few degrees off. Without times you won't have a composite Ascendant or houses, which are a large part of how astrologers read it.
Is a composite chart only for romantic partners?
No. It can be made for any two people: friends, siblings, colleagues or business partners. Some astrologers use it to understand a working partnership as much as a marriage.
What is the most important placement in a composite chart?
The composite Sun is usually read first, as the relationship's main purpose, with the composite Moon close behind as its emotional tone. Tight aspects to either of them are often the loudest themes in the chart.
