What a composite chart is
A composite is built by taking the midpoint of each pair of placements. Your Sun and their Sun produce a composite Sun somewhere between them; the same is done for every body and for the angles.
The result is not either person and it is not an average of two personalities. It is a third chart, read as the relationship itself, with its own Sun sign, its own ascendant and its own internal aspects.
Couples frequently recognise a composite faster than they recognise their synastry, because it describes the thing they are both inside rather than what each of them contributes.
How it differs from synastry
Synastry compares two charts and asks what touches what. It describes the pull between two people and the friction, and it is asymmetric: your Venus on their Saturn is a different experience from theirs on yours.
A composite collapses that asymmetry deliberately. There is no your-side and their-side; there is one entity with one set of positions. That makes it worse at describing how each person experiences the relationship and better at describing what the relationship is like from outside.
| Question | Which tool |
|---|---|
| What draws us together? | Synastry cross-aspects |
| Where does it play out? | Synastry house overlays |
| What is this relationship actually like? | Composite |
| What will other people see? | Composite ascendant and Midheaven |
Reading the composite Sun and ascendant
The composite Sun describes what the relationship is for: the thing it keeps returning to, the reason it exists as a unit. A composite Sun in the tenth house describes a partnership organised around work and public standing whether or not either person intended that.
The composite ascendant describes how the pair comes across. It is the couple version of a rising sign, and it is frequently more accurate about how friends describe you together than either person's own chart is.
Both need birth times, since the ascendant does. Without them you still get every planetary midpoint, which is most of the chart.
Aspects inside the composite
The angles between the midpoints are their own aspect set, and they are not inherited from either person. A composite can contain a tight square that neither individual chart has, and that square describes a tension belonging to the relationship rather than to a person.
This is the part of composite work that holds up best. Couples asked about a hard composite aspect usually name the recurring argument immediately, and it is often one neither of them would have predicted from their own charts.
The midpoint problem
Every midpoint has two solutions, since two points on a circle are separated by two arcs. Convention takes the shorter one, which is what this calculator does and what almost all software does.
There is a minority practice that takes the longer arc when the shorter one produces an implausible result, and there is a separate method called the derived or reference-place composite that computes the chart for a location rather than from midpoints. Neither is used here, and it is worth knowing they exist if you compare results with another tool and find a discrepancy.
What a composite cannot tell you
It does not predict whether a relationship lasts. No chart does, and composite readings that claim to are making a promise the technique cannot support.
It also has no sense of time. A composite for a couple who met last week and one for a couple of thirty years look identical if the birth data is the same, because nothing in the calculation knows when the relationship started. For timing, transits to the composite are the usual approach, and they are a more speculative technique than transits to a natal chart.
Using it alongside synastry
The productive order is synastry first, composite second. Synastry tells you what each person is bringing and where the contacts land; the composite tells you what the two of them add up to.
Where the two disagree, that disagreement is informative. A comparison full of easy synastry with a difficult composite describes two people who get on well and struggle to build anything, which is a real and recognisable pattern. The reverse describes a relationship that is hard work and somehow keeps functioning.
Common questions
What is a composite chart?
A third chart built from the midpoint of each pair of placements. It is not either person and not an average of two personalities; it describes the relationship as an entity with its own Sun, ascendant and aspects.
How is it different from synastry?
Synastry compares two charts and is asymmetric: your Venus on their Saturn differs from theirs on yours. A composite collapses that into one set of positions, which describes the relationship from outside rather than from either side.
Do we both need birth times?
For the composite ascendant and houses, yes. Without them you still get every planetary midpoint, which is most of the chart.
Can a composite predict whether we last?
No. It also has no sense of time: a composite for a couple who met last week looks identical to one for a couple of thirty years, because nothing in the calculation knows when the relationship began.
Why does my composite differ from another site?
Every midpoint has two solutions and convention takes the shorter arc, which is what this uses. Some tools take the longer arc in certain cases, and a separate method computes a composite for a location rather than from midpoints.
Which should I read first?
Synastry, then the composite. Where the two disagree is informative: easy synastry with a difficult composite describes two people who get on well and struggle to build anything.