Free tool
Composite Chart Calculator
A composite chart is one chart for the relationship itself, not a comparison of two people. Enter both sets of birth data to see where its planets sit, what angles they make to each other, and — when both birth times are known — its houses, Ascendant and Midheaven.
Enter both people's birth data
Person A
Your birth details are used only to calculate this chart. They are not saved.
Person B
Your birth details are used only to calculate this chart. They are not saved.
Still needed:Person A: Birth Date · Birth Time · Birth CityPerson B: Birth Date · Birth Time · Birth City
What a composite chart is
Take two birth charts, find the midpoint between each pair of matching planets, and plot those midpoints as a single chart. That chart is the composite. Astrologers read it as the relationship treated as a third thing with a chart of its own — a shared sky rather than two people compared. It is the same idea as saying a band has a sound that neither musician has alone.
What it is not
A composite chart does not say whether a relationship will last, whether two people should be together, or how it ends. It has no verdict in it. Nothing here is a prediction, and none of it should stand in for what the two people actually notice about each other. This page computes the geometry and stops there — the meaning is a reading, and readings are made by people, not by midpoints.
Composite or synastry?
Synastry compares the two charts: your Venus to their Mars, aspect by aspect, and where each person's planets land in the other's houses. The composite merges them into one chart instead. Most astrologers use both — synastry for what happens between two people, the composite for what the relationship is like from the inside.
Which composite this is
There is more than one convention, and schools disagree. This calculator uses the MIDPOINT composite: each composite planet is the shorter-arc midpoint of that planet in the two charts, and each composite house cusp is the shorter-arc midpoint of that same cusp in the two charts (the midpoint-of-cusps method), the Ascendant and Midheaven included. The other common method — the Davison relationship chart — casts a real chart for the midpoint in time and space between the two births, and gives different degrees. Neither is more correct; they answer slightly different questions, and we say which one you are looking at rather than choosing quietly.
Composite chart — questions
- What is a composite chart?
- A composite chart is a single chart built from the midpoints between two people's planets — the composite Sun sits halfway between their two Suns, and so on. It represents the relationship itself as one entity rather than two people interacting.
- Is this composite chart calculator free?
- Yes. Enter both sets of birth data and get the composite positions, houses and inner aspects instantly, with no account and nothing stored.
- Do I need both birth times?
- The composite planet positions and the aspects between them work from the two dates and places alone — except where the Moon is involved: without a birth time that person's Moon carries about twelve degrees of uncertainty, and the composite Moon half of it. The composite houses, Ascendant and Midheaven need both exact birth times — without them we show the positions and say so, rather than printing houses we can't calculate.
- What is the difference between a composite chart and synastry?
- Synastry measures the angles between two separate charts and where each person's planets fall in the other's houses. A composite merges the two charts into one. Synastry describes what happens between two people; the composite describes the relationship as its own entity.
- Midpoint composite or Davison chart?
- This tool computes the midpoint composite — the most widely used method. A Davison chart instead casts a real chart for the midpoint in time and place between the two births. The two give different degrees, and astrologers disagree about which to prefer; we tell you which one is on screen.
- Can a composite chart be retrograde?
- No. Composite planets are calculated midpoints, not bodies in motion, so there is no retrograde or direct motion to report. Any calculator that shows one for a composite is inventing it.
The conventions this chart uses
None of these are facts of the sky. Each is a choice astrologers disagree on, so we list ours — a difference from another site can then be traced to its rule instead of blamed on the stars.
- Tropical zodiac
- Signs are tropical, anchored to the March equinox, not to the constellations. Sidereal (Vedic) astrology counts from the stars instead, which currently shifts every position by about 24 degrees — the most common reason two sites disagree about a sign.
- Placidus houses
- Houses are Placidus, the most widely used modern system. Whole-sign or Koch redraw the boundaries: they move planets between houses, never between signs. Beyond the polar circles Placidus is undefined, and we then show the chart without houses rather than guess.
- Mean lunar nodes
- The lunar nodes are mean (averaged). The "true" node oscillates around the mean by up to about two degrees — measured, at most 1°59' across two centuries.
- Mean Lilith
- Black Moon Lilith is the mean lunar apogee. The "true" (osculating) variant can sit up to about thirty degrees away — often a different sign, and the single biggest source of Lilith disagreements.
- Aspect orbs
- Natal orbs: conjunction and opposition 8°, square and trine 7°, sextile 5°, quincunx 3°. Toward the Ascendant and Midheaven the orbs tighten, and the quincunx is not counted there at all. A site with wider orbs lists more aspects, not different planets.
- Sect
- The Part of Fortune follows sect: a day birth (Sun above the horizon) uses Ascendant + Moon − Sun, a night birth the reverse. For night births, calculators that apply the day formula to everyone place it in a different sign roughly nine times out of ten.