Synastry vs Composite Chart: Two Ways to Compare Charts
Synastry and composite charts are both used to explore relationships in astrology, but they answer different questions. Synastry compares two people’s charts with each other; a composite chart blends them into a single chart for the relationship itself. This guide explains how each works, adds the Davison chart and shows when each is useful.
Your next step
Start with each person’s own birth chart. You can create both free on Start, with permission from the other person to use their details.
Synastry: comparing two charts
Synastry keeps the two birth charts separate and looks at how they interact. Astrologers examine inter-aspects (angles between one person’s planets and the other’s) and house overlays (where one person’s planets fall in the other’s houses). It is read in both directions, because your Venus to their Mars is a different contact from their Venus to your Mars.
Synastry is useful for exploring how two people might experience each other. Our synastry chart guide covers inter-aspects and overlays in more detail.
Composite chart: one chart for the relationship
A composite chart combines two charts into one by taking the midpoint of each pair of matching planets. If one person’s Sun is at 10° Aries and the other’s is at 10° Gemini, the composite Sun is at 10° Taurus. The process is repeated for every planet, and the angles are usually derived from midpoints too, which means it needs both birth times for the Ascendant and houses.
The midpoint composite was popularised by Robert Hand’s 1975 book Planets in Composite. It is read as a symbol of the relationship as its own entity, with its own themes, rather than as either person.
A quirk of midpoints
Every pair of points has two midpoints, opposite each other. Composite charts conventionally use the nearer one. Composite charts also cannot be located in real time and space; they are a mathematical construct, read symbolically.
Davison chart: the midpoint in time and space
A Davison chart, introduced by Ronald Davison in 1977, takes a different route. It finds the midpoint between the two birth dates and times, and between the two birthplaces, and calculates an ordinary chart for that moment and location. Because it is a real chart, it has real planetary positions and houses.
Composite and Davison charts often show similar themes but can differ in detail. Some astrologers prefer one, some use both.
One relationship, two methods: an example
Imagine two people, whom we will call Alex and Sam. This is an invented example to show the methods, not a reading of real people.
In synastry, an astrologer might notice that Sam’s Venus at 18° Cancer sits close to Alex’s Moon at 20° Cancer, a conjunction often read as a sense of warmth and care between them. Alex’s Mars might square Sam’s Sun, which could be read as energy that sometimes feels like friction.
In the composite, those Moons combine differently. If Alex’s Moon is at 20° Cancer and Sam’s is at 2° Virgo, the composite Moon falls at their midpoint, 11° Leo. The astrologer would read that composite Moon as part of what the relationship itself seems to need, perhaps warmth and shared enjoyment, rather than as either person’s feelings.
The two methods are describing the same pair from different angles. Synastry asks how Alex and Sam affect each other; the composite asks what the “we” is like.
How to start reading a composite chart
A composite chart is read much like a birth chart, with the relationship as the subject. A simple order:
- Composite Sun: what the relationship seems to be about, its central purpose or theme.
- Composite Moon: what helps the relationship feel safe and settled.
- Composite Ascendant: how the relationship may appear to others (this needs both birth times).
- Houses: which areas of life the relationship focuses on, such as home, work or shared resources.
- Aspects: how the composite planets support or challenge each other.
The 12 houses guide explains each house if you want to read composite house placements.
Synastry vs composite: which to use
- Use synastry to explore how each person might experience the other: what flows easily, where friction may appear, and how needs compare.
- Use a composite or Davison chart to reflect on the relationship as a shared project: what it seems to be about, and where it puts its energy.
- Use both for a fuller picture, starting with each natal chart, then synastry, then the composite.
None of these methods can tell you whether a relationship will last or whether you should stay together. They can prompt better conversations. For a broader view, read birth chart compatibility and love astrology.
Beyond romance: friends, family and work
Synastry and composite charts are not only for couples. People also use them to reflect on friendships, parent and child relationships, siblings and working partnerships. A business partnership composite, for instance, might be read for how the two people share responsibility and make decisions together.
The same care applies in every case: ask permission before using someone’s birth details, and use the charts to open a conversation rather than to explain away a difficulty.
Birth times, permission and uncertainty
Synastry inter-aspects between planets need only birth dates, but house overlays need the time of the person whose houses are used. Composite and Davison Ascendants and houses need both times. If either time is unknown, focus on planets and aspects and leave houses aside; see birth chart without birth time.
Always ask before entering someone else’s birth details, and keep the comparison as a shared exploration rather than a verdict about them.
A few useful answers
What is the difference between synastry and a composite chart?
Synastry compares two separate charts; a composite chart combines them into one chart using planetary midpoints, read as the relationship itself.
What is a Davison chart?
A real chart calculated for the midpoint in time and location between two people’s births, used like a composite chart.
Do I need birth times for a composite chart?
For planet positions, dates are enough. For the composite Ascendant and houses, both birth times are needed.
Can a composite chart predict if a relationship will last?
No. It can offer themes for reflection and conversation, not a prediction of the outcome.
Which is better, a composite or a Davison chart?
Neither is better by rule. Composite charts use planetary midpoints; Davison charts are real charts for a midpoint moment and place. Many astrologers compare both.
Can I use synastry and composite charts for friendships?
Yes. The same methods are used for friends, family and working partnerships, always with the other person’s permission.
Explore your next question
Start with your own chart, then explore the comparison.