What synastry is, in one sentence
Synastry is the technique of comparing two birth charts to see how the planets in one chart talk to the planets in the other. It’s the closest thing astrology has to a relationship microscope. It doesn’t tell you whether to be with someone; it tells you what the connection between you is actually made of.
The first thing to compare: your luminaries
The Sun and Moon are called the luminaries, and they carry the most weight in synastry. The relationship between your Sun and your partner’s Moon (and vice versa) tells you whether your essential self and their inner world recognise each other. Sun-Moon contacts in synastry are some of the most enduring; partners with these often describe a feeling of “finally being known”.
The Rising overlay: how you arrive at each other
Your Rising sign sits at the cusp of your first house. When your partner’s Sun or Moon falls in that area of your chart, they activate your sense of self in a way that’s hard to describe but easy to feel. Rising overlays often explain the magnetism of a first meeting; you couldn’t quite say why, but you couldn’t quite look away either.
Venus and Mars: love and desire
Venus is how you love; Mars is how you want. In synastry, the contacts between your Venuses and your Marses describe the chemistry of the relationship. Venus-Mars connections between two charts can produce strong sexual attraction. Venus-Venus connections describe whether your love languages match. Mars-Mars describes how you’ll fight and how you’ll move toward shared goals.
The aspects between charts: the live wires
The angles your planets make to each other’s planets are where synastry gets specific. Soft aspects (trines, sextiles) describe ease and natural flow. Hard aspects (squares, oppositions) describe tension and growth. Conjunctions describe blending and amplification. A relationship with only soft aspects can feel pleasant but stagnant; a relationship with only hard aspects can feel exhausting. The most enduring partnerships usually have a mix.
What synastry can’t tell you
Synastry tells you what the connection is made of, but not whether you should pursue it. Charts with stunning compatibility can still end badly when people make poor choices; charts with significant friction can flourish when both partners do the work. The chart describes the wiring; the relationship is still up to you.
The fastest way to read your own
Use the free compatibility calculator on this site for a starting reading based on your two Sun signs and your element conversation. For the full synastry analysis, the personal compatibility report covers Venus and Mars, the Moons, your houses overlay, and the major aspects between the two charts.