Composite Chart Calculator
A composite chart is a single chart built from two, by taking the midpoint of every matching pair of planets. It describes the relationship itself as its own entity — not how either person experiences the other, which is what a synastry chart shows. Enter both sets of birth data below.
How a composite chart is built
Every planet in a composite chart is the short-arc midpoint between that planet in the two natal charts — the composite Sun sits halfway between the two natal Suns, the composite Moon halfway between the two Moons, and so on. Nobody was born at that moment. The chart is a construction, and it is read as a portrait of the partnership rather than of either partner.
Reading the result
The composite Sun describes what the relationship is for — its purpose and the thing it keeps returning to. The composite Moon describes what it needs emotionally to feel safe. The composite Ascendant is how the pair comes across to everyone else, which is often the part that surprises the two people inside it. Venus–Mars contacts describe the romantic and physical dynamic.
Questions people ask
How is this different from synastry?
Synastry lays two charts over each other and reads the contacts between them: how each person experiences the other. A composite collapses the two into one chart and reads the thing they make together. Most readings use both — synastry for the chemistry, composite for what the relationship turns into. You can run the same two people through the synastry calculator and compare.
Do both birth times need to be accurate?
For the planets, no — a few hours either way barely moves them, so the composite Sun, Moon and the aspects between planets stay reliable. For the composite Ascendant, Midheaven and houses, yes: those are built from both birth times, so an error in either one carries straight through. If one time is a guess, read the planets and ignore the houses.
Does it work for friendships and business partners?
Yes. Nothing in the method is romantic — it is the midpoint of two charts, whatever the two people are to each other. The Venus and Mars material simply matters less when the partnership is not one.
Related: Synastry vs. Composite · Synastry and Compatibility · Planets in Signs