What is synastry
Synastry is the comparison of two natal charts: the classic astrological tool for reading a relationship. Here is how it works and what it is for; to calculate your own compatibility, head to the calculator.
Calculate your synastryWhat is synastry
Synastry is the comparison of two natal charts. You take the first person’s planets and bring them into contact with the second person’s, measuring the angles they form: conjunctions, trines, squares, oppositions. Each angle describes a different way two energies meet, support or challenge each other.
Unlike a horoscope, which looks at a single chart, synastry reads the relationship as a two-body system. It is the classic astrological tool for understanding why something clicks with certain people and not with others.
How to read it
Contacts between the personal planets, Sun, Moon, Mercury, Venus and Mars, tell the most immediate part of the bond: identity, emotions, dialogue, affection and desire. The slower planets add the backdrop: commitment, growth, transformation.
Every contact has a tone. Trines and sextiles flow easily, squares and oppositions create friction, and friction is not necessarily bad: often it is exactly the tension that keeps a relationship alive.
Themes and affinity
To make all of this readable, the contacts are grouped into five themes: chemistry, communication, values, growth and tension. Each measures how active that force is between the two people.
The overall affinity combines the four constructive themes and treats tension as a mild weight, not a veto: an intense but connected pair is worth more than a flat one. It is an orienting number, a starting point for reading the rest.
Frequently asked questions
What is synastry?
Synastry compares two natal charts to read the relationship between two people. Instead of looking at a single chart, it puts one person’s planets against the other’s and measures the angles they form: these contacts are what tell chemistry, friction and underlying affinity. It is the classic astrological tool for understanding how two people fit together.
Do I need the birth time?
Yes, a complete synastry needs the birth time of both people, together with the place. The time sets the Ascendant and the houses, which weigh heavily when comparing two charts. Without the time the calculation stays partial and some important contacts cannot be assessed.
Does it work for friendship too?
Yes. Synastry is not only about couples: the same contacts read in the key of friendship, family or collaboration. You can choose a romantic or a friendship reading, and the full report adapts its tone accordingly.
What do I see for free?
For free you see the overall affinity, the five relationship themes and the aspects that define the bond: enough to get a concrete sense of the connection. The full paid report adds the discursive explanation of every aspect and a personalized analysis of the pair.
How reliable is it?
It is a symbolic tool for reflection, not a scientific prediction about the fate of a relationship. It helps bring dynamics, strengths and frictions into focus, the kind worth thinking about. It is worth as much as the awareness you bring to it, not a verdict on the future.
Explore the rest of Cosmic Love
Synastry is just one of the maps. On Cosmic Love you also find your Destiny Matrix, numerology, natal chart, tarot and much more.