Free Astrology Calculator
Composite Chart Calculator
Make one chart for a relationship. Enter both people's birth details for the midpoint composite chart, or switch to the Davison chart cast for the moment and place halfway between the two births, with positions, houses and aspects.
What a Composite Chart Shows
Two people in a relationship create something neither has alone: shared habits, a shared mood, a way of being seen together. A composite chart describes that third thing. It is built from the midpoints between the two birth charts, planet by planet, and read like a birth chart for the relationship. The composite Sun describes what the relationship is for, the Moon what it needs to feel safe, Venus how affection moves in it, and the Ascendant how it meets the world.
How the Midpoints Work
Each planet sits at the nearer midpoint of the two positions. Two Suns at 10° Aries and 10° Gemini give a composite Sun at 10° Taurus; two Moons at 28° Pisces and 2° Aries give a composite Moon at 0° Aries, because the shorter arc crosses the start of the zodiac. Houses use the same rule on each cusp, with the Ascendant and Midheaven as the midpoints of the two charts' angles.
The Davison Chart
The Davison chart takes a different route to the same question. It finds the moment exactly halfway between the two births in time, and the point halfway between the two birthplaces on the globe, and casts an ordinary chart for that moment and place. Its planets are where they really were, so its aspects and houses work like those of any birth chart. Switch the method above to see it.
Reading a Relationship Chart
- Begin with the Sun, Moon and Ascendant. Together they describe the relationship's purpose, its emotional life and its outward style.
- Notice the houses. A composite Sun in the 4th house gathers a relationship around home and family; in the 10th, around shared work and public life.
- Look at the aspects. Hard aspects in a composite chart describe the relationship's recurring tensions, and easy ones the places where it rests.
- Hold it lightly. The chart describes a quality the two of you share. How you live it is your choice, and it can change as you do.
To compare the two charts sign by sign, use the birth chart compatibility calculator.
Composite Chart Questions
What Is a Composite Chart?
A composite chart is one chart made from two. For each planet, it takes the midpoint between the two people's positions: if one Sun is at 10 degrees Aries and the other at 10 degrees Gemini, the composite Sun is at 10 degrees Taurus. The result is read as a portrait of the relationship itself, the third thing two people create together.
How Is a Composite Chart Different From Synastry?
Synastry keeps the two charts separate and shows how each person's planets touch the other's. A composite chart merges them, so it describes the relationship as a whole: its purpose, emotional life and style. Many astrologers read synastry for how two people experience each other and the composite for what they build.
What Is a Davison Chart?
A Davison chart, introduced by the astrologer Ronald Davison in 1977, is a real chart cast for the moment halfway between the two births and the place halfway between the two birthplaces. Every planet sits where it actually was at that moment, so the chart behaves like a birth chart, with real aspects and real house cusps.
Composite or Davison: Which Should I Use?
Both are widely used and they usually agree on the broad themes. The midpoint composite is the more common and is what most astrologers mean by composite. The Davison chart is preferred by those who want a chart that could exist in the sky. When two people were born years apart, the slow planets can differ between the two methods, so it is worth looking at both.
How Are Composite Houses Calculated?
This calculator uses midpoint houses: each house cusp is the midpoint of the two charts' matching cusps, and the Ascendant and Midheaven are the midpoints of the two Ascendants and Midheavens, with the Ascendant kept on the eastern side of the chart. That needs both birth times. The Davison chart has ordinary houses for its date and place.
Can I Make a Composite Chart Without Birth Times?
Yes. The planets of a composite chart come from the dates, so they are reliable without times, apart from the Moon, which can shift several degrees. Without both birth times there are no composite houses, Ascendant or Midheaven, and the calculator marks the Moon as approximate.
Why Can the Composite Sun Fall Far From Either Person's Sun?
Every circle has two midpoints between any two positions, and the composite uses the nearer one. When two planets are almost opposite, the nearer midpoint can land in a sign neither person has. Mercury and Venus can also end up in signs that would be impossible in a single chart, which is one reason some astrologers prefer the Davison chart.