Synastry Chart Calculator

Synastry puts two birth charts side by side and looks at the angles between them. Give both birth dates, with the times and places if you have them, and this works out the Sun, the Moon, Mercury through Pluto, the mean lunar node, the ascendant and the midheaven for each person, then lists every conjunction, opposition, trine, square, sextile, quincunx and semisextile between the two charts with its orb. Positions are computed from published orbital elements rather than read from a table, and were checked against dated events: the great conjunction of December 2020, the eclipse of April 2024 and the Pluto ingress of March 2023 all come out where they belong. House cusps are not computed, because which house system to use is an argument among astrologers rather than a calculation.

Calculator Type

Birth date, time and place for both people. The time and place are only needed for the ascendant, the midheaven and the last degree or so of the Moon; every planet is in the same sign everywhere on Earth at the same moment.

Person A Birth Date (YYYY-MM-DD) *

Person A Birth Hour on the Local Clock (0-23)

Person A Birth Minute

Person A UTC Offset of the Birth Place (hours)

Negative west of Greenwich. Include daylight saving if it was in force that day.

Person A Birth Latitude (negative south)

Between 66 south and 66 north. Inside the polar circles the ascendant stops behaving and this will not pretend otherwise.

Person A Birth Longitude (negative west)

Person B Birth Date (YYYY-MM-DD) *

Person B Birth Hour on the Local Clock (0-23)

Person B Birth Minute

Person B UTC Offset of the Birth Place (hours)

Negative west of Greenwich. Include daylight saving if it was in force that day.

Person B Birth Latitude (negative south)

Between 66 south and 66 north. Inside the polar circles the ascendant stops behaving and this will not pretend otherwise.

Person B Birth Longitude (negative west)

Widget