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 house method uses the midpoint MC and the mean birth latitude, as explained below. 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 shorter-arc midpoint between that planet's positions in the two natal charts. At exact opposition, both midpoint choices are equally distant; Augurine selects the one with the smaller longitude measured from 0° Aries. Swapping the people preserves every composite position.

The composite Midheaven uses the same midpoint rule. We erect one house system from that MC at the mean of the two birth latitudes, using the mean true obliquity of the two natal charts. This tool requests whole sign houses: the resulting Ascendant's sign is the first house, and each following sign is the next house. The MC remains a separate angle and can fall outside the tenth house. The direct midpoint of the natal Ascendants is displayed as a separate sensitive point. Every planetary house assignment uses the resulting composite cusps.

Both accurate birth times are needed for the displayed angles and houses. Without them, the calculator still gives planetary positions and aspects, with greater uncertainty for the fast-moving Moon. Other placements close to a sign boundary or aspect limit can also change within the possible birth-time range.

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 Sun is commonly read for the relationship's core purpose and the identity it projects into the world. The composite Moon is 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.