Free Composite Chart Calculator

A composite chart is a single symbolic chart for a relationship, built by taking the midpoint between each pair of planets in two birth charts: your Sun and their Sun, your Moon and their Moon, and so on. Astrologers read it as one chart for the bond itself rather than for either person alone.

This composite chart calculator computes that midpoint chart for you: every planet, the composite Ascendant and Midheaven, the house cusps when both birth times are exact, and the aspects the composite planets make to each other. The midpoint approach was popularized by astrologer Robert Hand in his 1975 book Planets in Composite, and it stays the method most Western astrologers mean when they say composite chart. Each result is drawn from two natal charts, so the more accurate your birth data, the sharper the midpoint chart.

Three techniques get grouped under relationship astrology, and they answer different questions. Synastry keeps both birth charts intact and measures how one person's planets touch the other's, so it reads the chemistry between two people. A composite chart averages the two charts into one midpoint chart for the relationship as its own entity. A Davison chart also produces one relationship chart, but instead of averaging planet positions it finds the midpoint in time and space between the two births and casts a real chart for that moment.

Reach for synastry when you want to see attraction and friction between two people, and for the composite or Davison when you want a picture of the relationship itself. Because the Davison chart is cast for an actual date and place, many astrologers run transits and progressions against it, which the composite's abstract midpoints do not support as cleanly. You can build every version here and compare what each one says.

Each composite planet sits at the near midpoint between the same planet in both charts. The composite Sun is the midpoint of the two Suns, the composite Venus the midpoint of the two Venuses, and the pattern holds for every body and point. The Sun/Moon midpoint carries extra weight in relationship work, which is why it also has its own calculator.

Astrologers differ on how to derive the composite Ascendant: some take the direct midpoint of the two Ascendants, others derive it from the composite Midheaven so the angles stay geometrically consistent. Either way both accurate birth times are required, so the composite Ascendant, Midheaven, and house cusps appear only when you enter exact times for each person. You can still calculate a composite chart without a birth time. The planet signs and the aspects between them depend on the date rather than the clock, so they stay reliable; the composite Moon, angles, and houses are the parts that move when a birth time is uncertain.

Once you calculate, the results label every composite placement and link straight to a sign and house reading for each one, so you can work through the chart piece by piece. Start with the composite Sun. Its sign and house are commonly read as the relationship's core identity prompt and primary area of focus. A composite Sun in the 7th house, for example, centers the relationship around partnership and mutual commitment, while a 10th house Sun suggests the relationship has a public-facing quality or shared ambition. The composite Moon shows the emotional undercurrent: how both people feel when they're together and what the relationship needs to feel safe.

Angular planets, those near the composite Ascendant, MC, Descendant, or IC, often stand out in the relationship's expression. Venus or Jupiter angular can indicate a relationship others perceive as warm, generous, or fortunate. Saturn angular can feel heavy but may build lasting structure. The internal aspects between composite planets show whether the relationship's energies flow easily (trines, sextiles) or generate tension that drives growth (squares, oppositions). A composite chart with many squares is not automatically a bad sign; it usually means the relationship pushes both people to evolve.

The composite Sunis commonly read for the relationship's core purpose and the identity it projects into the world. The composite Moonis read for emotional tone: what the relationship needs to feel secure and how both people may feel when they're together. Composite Venus shows how love and affection may be expressed between you: the style of tenderness, generosity, and aesthetic pleasure the relationship generates. Composite Mars governs how desire and conflict operate: whether friction is approached directly, passively, or productively. Composite Saturn can act as glue; its sign and house show where the relationship demands patience and structure, but also where it builds the most enduring foundation.

House placements matter as much as signs. A composite Venus in the 2nd house orients love around shared resources and security; in the 5th it's playful and expressive; in the 8th it's intense and transformative. Any planet in an angular house (1st, 4th, 7th, or 10th) will color the relationship's visible personality more than one tucked in a cadent house. For full sign-by-sign and house-by-house interpretations of every composite placement, visit our composite chart interpretation guide.