Free Composite Chart Calculator for Two Birth Charts

Enter the birth details for Person A and Person B to calculate a composite chart. The result treats the two charts as a pair: it is read as a picture of the people together, not as either person's birth chart. The composite chart uses the midpoint of each matching point, such as the Sun in A's chart and the Sun in B's. Its placements describe themes the two people may recognize in how they relate.

Each pair of points has two possible midpoints, opposite each other; the calculator uses the one on the shorter arc. For example, points at 350° and 10° give a midpoint at 0°, not 180°. The Ascendant and Midheaven are included only when both birth times are known. If the near Ascendant midpoint falls on the wrong side of the Midheaven, the opposite point is used. Houses are Equal houses counted from the composite Ascendant, each 30 degrees wide, rather than either person's house system.

The result includes a chart wheel, a table of composite points, and the aspects those points make to one another. It covers the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, and the north node. Beside each composite point, the table shows the position in Person A's chart and the position in Person B's chart. An aspect is the angular relationship between points; these links are read with the same orbs used for other chart aspects.

Without both birth times, the composite Ascendant, Midheaven, and houses cannot be calculated. The planets still have composite positions, shown as possible signs when the missing time leaves uncertainty. The Moon is the point most affected: its composite position can vary by up to about seven degrees either way, while the Sun can vary by a quarter of a degree. The listed possibilities show the range tied to the unknown time, not a single confirmed placement.