Birth Chart Compatibility Calculator
Comparing two sun signs tells you very little, because a sun sign is one of ten placements and the interesting part of astrological compatibility is not what you each are — it is what happens where the two charts touch. This computes both charts and reads the contacts between them.
The eight phases
Where a life sits in the lunar cycle, and what the tradition makes of each position.
Easy
Mostly harmonious contacts. Comfortable and low-friction, which is pleasant and occasionally inert — pairs like this sometimes lack the tension that makes people bother to change.
Warm
More support than friction. The difficult contacts are there but outnumbered, which is roughly the shape of most durable relationships.
Mixed
Support and friction in similar measure. This is the most common result and the least conclusive; what it means depends entirely on which contacts fall where.
Effortful
More friction than ease. Not a verdict against the pair — plenty of long marriages read like this — but it does mean the relationship is unlikely to run on autopilot.
Abrasive
Predominantly hard contacts. Intense and rarely dull. Worth being specific with each other about where the friction actually sits, because this configuration does not resolve by being ignored.
Common questions
What is a synastry chart?
Two birth charts laid over each other so the angles between one person's planets and the other's can be measured. Those cross-aspects are the substance of astrological compatibility: an aspect inside your own chart describes you, while an aspect between the charts describes the contact between you.
Do we both need our birth times?
No, and the reading tells you what you lose without them. Contacts involving the Sun, Mercury, Venus, Mars and the outer planets are effectively unaffected, because none of them move far in a day. The Moon is the exception — it covers about thirteen degrees daily, so a Moon contact can appear or disappear depending on the hour.
What is a good compatibility score?
There is no calibrated answer, and any site presenting one to a decimal place is inventing precision. The score here summarises the contacts listed beneath it and nothing more. Long relationships routinely contain plenty of difficult aspects; what tends to matter is whether the friction is somewhere both people can name.
Which aspects matter most in synastry?
Traditionally the personal-planet contacts: Sun to Moon for long-term ease, Venus to Mars for attraction, Moon to Saturn for the pattern where one person's need for reassurance meets the other's instinct to withhold it. Contacts between two outer planets are shared by everyone born in the same few years and say little about a specific pair.
Is this different from sun sign compatibility?
Yes, and considerably more specific. Sun sign compatibility compares two of the twelve signs and produces one of 144 possible answers. This compares ten bodies against ten, so two people who share a sun sign pairing can get quite different readings depending on where everything else fell.