What is a composite chart? How to read a relationship chart
Updated: 1 November 2026
A composite chart is a single “relationship chart” created from two people’s birth charts. Where synastry answers “how do we affect each other?”, the composite chart answers “what is this relationship like?”
How is a composite chart calculated?
For each planet, the midpoint between the two people’s positions is taken. If one person’s Sun is at 10° Aries and the other’s is at 20° Gemini, the composite Sun falls exactly halfway between, at 15° Taurus. The same is done for the Moon, Venus, Mars and the other planets. The result is a new chart that treats the relationship as having a character of its own.
This is called the midpoint method, and it is the most widely used way to build a composite chart. Astro Sinastri uses it too.
Synastry or composite?
| Synastry | Composite chart | |
|---|---|---|
| What does it look at? | How two people affect each other | The relationship’s own character |
| How? | Two charts overlaid | One chart from midpoints |
| Which question does it answer? | “How do we make each other feel?” | “What are we like as a whole?” |
The two complement each other. A couple can have strong attraction in synastry and a demanding composite chart, or the other way round. The fullest picture comes from looking at both.
The key points in a composite chart
- Composite Sun: the core of the relationship. Its purpose, identity and what it revolves around. A composite Sun in Taurus, for example, describes a relationship built on trust and stability.
- Composite Moon: the emotional climate. How feelings play out when you’re together and how safe you feel in the relationship.
- Composite Venus: the relationship’s love language. How you show each other love and the style of your romance.
- Composite Mars: your shared energy. How you act, decide and argue together.
- Composite Ascendant: how others see you. How other people perceive you as a couple. Requires both birth times.
Aspects in a composite chart
Planets in a composite chart form aspects with each other too, but this time the aspects are inside the relationship rather than between two people. A harmonious aspect between the composite Sun and Moon, for instance, shows that the relationship’s purpose and its emotional needs are in tune. An aspect between composite Venus and Saturn describes a relationship shaped by seriousness and loyalty.
For the general meaning of each aspect, see the synastry aspects guide; the same aspect types are read in a similar way in a composite chart.
The limits of a composite chart
A composite chart doesn’t belong to a real moment in the sky; it is derived mathematically. Astrology itself is not a science either. A composite chart is at its best as a starting point for thinking of your relationship as a “third person” and talking about what it needs.
Frequently asked questions
What is the difference between a composite chart and synastry?
Synastry overlays two charts and looks at how each person affects the other, as in ‘your Venus touches my Mars’. A composite chart creates a single chart from the midpoints of both charts and describes the relationship itself, as if it were a person of its own.
Do you need birth times for a composite chart?
Composite planet positions can be calculated without birth times. The relationship’s Ascendant and houses, however, need both people’s birth times, and without them the Moon may be off by a few degrees.
Are difficult aspects in a composite chart bad?
No. Squares and oppositions in a composite chart show the areas the relationship needs to work on. Every relationship has easy sides and sides that take effort.