Composite Chart: Two People Merged into One Chart of the Relationship
A synastry chart overlays two charts to see where your planets touch the other person’s. A composite chart merges them into one: the midpoint of your two Suns becomes the composite Sun, the midpoint of your two Moons the composite Moon, and so on for all ten planets. The result belongs to neither of you; it describes what you are like together. Cast your composite chart first, then read it with the guide below.
Free Composite Chart Calculator
Enter both people's birth dates, birth times and birthplaces. The calculator takes the midpoint of each pair of planets and casts a single chart for the relationship itself: the composite Sun, Moon, Ascendant and Venus are read one by one, the key aspects inside the chart are listed, and you are warned if the composite has unstable midpoints or positions the real sky could not produce. It works without birth times too; you just lose the Ascendant and houses. Everything is calculated in your browser; nothing is uploaded.
Tropical zodiac, near-midpoint method. The Midheaven is the midpoint of the two Midheavens; the Ascendant and house cusps are derived from the composite Midheaven at the average latitude of the two birthplaces (Placidus). Enter the local clock time on each birth certificate; daylight saving time is removed automatically from the birthplace.
How a composite chart is calculated
Planets: for each planet, take the two people’s positions on the zodiac and find the point halfway along the shorter arc between them, the “near midpoint”. For example, if one Sun is at 10° Aries and the other at 20° Gemini, they are 70° apart, and the midpoint is 15° Taurus.
Midheaven and Ascendant: the Midheaven is likewise the midpoint of the two Midheavens. If the Ascendant were also taken as a plain midpoint, it often would not fit with the Midheaven, so the usual method (proposed by Robert Hand and used by most astrology software) derives the Ascendant and house cusps from the composite Midheaven at the average latitude of the two birthplaces. In our calculation for pairs born in Taipei, the two ways of finding the Ascendant land in the same sign about 83.8% of the time, 12° apart on average, but occasionally they end up in opposite signs. The calculator warns you when they differ.
There is also the “time-space midpoint chart” (the Davison chart), which takes the midpoint of the two birth moments and places and casts a chart of a real moment in the sky. That is a different technique from the midpoint method on this page.
How it differs from synastry
| Synastry (chart comparison) | Composite chart | |
|---|---|---|
| What it looks at | One person's planets touching the other's | A single chart merged from both, read as the relationship's own birth chart |
| Number of charts | Two charts overlaid | One new chart |
| Question it answers | How do I feel about you, and how do you affect me? | What are we like together, and where is this relationship heading? |
| Direction | Directional: your Venus, my Mars | No direction: swapping person A and B gives the same result |
| Our calculator | Synastry Chart | This page |
The two work well together: synastry shows how two people act on each other, and the composite shows the personality of the relationship once they are combined. Many astrologers look first at the attraction and friction in the synastry, then use the composite to see where the relationship is best suited to go.
Start with these four placements
- Composite Sun sign: the core purpose of the relationship and what you are like as a pair.
- Composite Sun house: which area of life the relationship centers on: the 7th house is the relationship itself, the 10th working together and your public image, the 4th home. Needs both birth times.
- Composite Moon: the emotional atmosphere between you, how you make each other feel safe and how you make up after a fight.
- Composite Ascendant: the first impression the relationship gives others, often reflecting how it began. Needs both birth times.
Then look at the composite Venus (how you enjoy things together) and a few key aspects inside the chart. The table below is our own calculation: the share of random pairs whose composite chart has that aspect within orb.
| Contact | About | Composites of random pairs with this aspect |
|---|---|---|
| Sun–Moon | Are Your Goals and Feelings in Sync? | 38.1% |
| Venus–Mars | The Rhythm of Attraction and Action | 28.8% |
| Moon–Venus | The Warmth and Sweetness of Everyday Life | 39.7% |
| Sun–Jupiter | The Scope of Growing Together | 37.7% |
| Sun–Saturn | The Weight of Commitment and Responsibility | 40.4% |
| Moon–Saturn | A Safe Emotional Distance | 38% |
| Venus–Saturn | Love Meets Reality | 28.8% |
| Venus–Pluto | Depth and Control in Love | 31.8% |
Charts of people born in Taipei between 1960 and 2005, paired at random, 2,100 pairs in all, calculated by our engine with the same orbs as a natal chart. A composite chart has 25.5 aspects on average.
The composite Sun in the twelve signs
| Composite Sun | What the relationship is like |
|---|---|
| Aries | At its core, this relationship is about starting things together. When you two team up, everything speeds up. An idea turns into action almost immediately, and a sign-up, a move, or a career change often gets decided right after one of you says, “Well, let’s try it.” You feel most alive facing something new, with a project that has only just begun. When life gets too smooth, things can go stale, so it helps to keep finding each other a fresh goal. |
| Taurus | The relationship centers on building a steady life. You two are most at ease over a good dinner, on a comfortable couch, or watching savings grow little by little. Neither of you feels any rush to prove anything; trust builds one day at a time. As a working partnership, this tends to be the patient, results-minded kind. The thing to watch is that once habits settle in, the two of you may not want to budge. |
| Gemini | This relationship runs on conversation. Messages fly back and forth all day, and the moment either of you reads an interesting article or hears something odd, the first impulse is to send it to the other. Together your minds move fast, and talk can jump from breakfast to world news. Taking a class or browsing a bookstore together suits you well. Curiosity feeds this bond, so when the talk thins out, it is usually time to go find something new together. |
| Cancer | The heart of this relationship is care and belonging. Being together tends to feel like home. Whoever gets back late finds a light left on, and whoever feels unwell can count on something warm on the stove. You both care a great deal about each other’s families and histories, and you easily put the other’s feelings ahead of your own. That tenderness is the foundation here; just remember that holding on too tightly leaves little room for each of you to grow. |
| Leo | This relationship likes to be seen. You two carry a certain glow when you show up together. You are often the ones organizing the get-together, and birthdays and anniversaries call for a real occasion. At its core the bond is about mutual admiration: each of you needs to know you are special in the other’s eyes. Creative projects you can share with others warm things up the most, while a steady diet of chores and errands leaves you both feeling something is missing. |
| Virgo | The purpose of this relationship often comes down to doing things well together. You two are practical with each other, and schedules, chores, and even how the closets are organized tend to follow rules you both quietly agree on. You show you care by doing: restocking what the other has run out of, giving their paperwork a second read. That attentiveness keeps life orderly. Just be careful not to turn a critical eye on each other, so that concern starts to sound like correction. |
| Libra | This relationship is built around balance and fairness. You two talk decisions through, and whoever gives ground this time can expect the favor returned next time. Together you come across as gracious, and you care that the relationship looks harmonious; friends often see you as a couple who really know how to get along. Your greatest strength is working things out. What needs practice is saying out loud what actually bothers you, instead of pushing problems down the road to keep the peace. |
| Scorpio | This relationship wants depth. You two easily develop an understanding no one else can break into. Some things you say only to each other, and some things only the two of you know. At its core the bond is about trust and carrying things together, and getting through a hard stretch side by side draws you closer. Because the connection is so strong, you are especially sensitive to secrets. Saying plainly what matters to you settles things far better than quietly watching each other. |
| Sagittarius | This relationship is like a journey you set out on together. Weekends go to planning the next trip, signing up for a course, or reading the same book and then arguing over its ideas. Together your horizons widen, and you are both more willing to try the unfamiliar. Growth and meaning feed this bond, and it needs some freedom on both sides; hold on too tightly, and the light in this relationship starts to dim. |
| Capricorn | This relationship is like building a house together. You two naturally think long term, and saving, buying property, and career plans tend to happen step by step, on a schedule. You rarely make a show of your feelings; your commitment shows in what you do and what you take responsibility for. The longer you are together, the more weight the relationship carries, and others often see you as dependable. Beyond the goals, remember to set the plans aside now and then and simply enjoy being together. |
| Aquarius | At its core, this relationship is about being yourselves and being friends. You two respect each other’s space, each with your own circles and interests, yet you often find yourselves surprisingly in tune on certain ideals. To outsiders your pairing may look a little unusual, since it does not follow the usual script. You are most alive when you throw yourselves into a community or an idea together. The thing to watch is that when feelings get too rational, the other person may not feel the warmth. |
| Pisces | This relationship carries a connection that is hard to put into words. You two often sense what the other has left unsaid, and listening to music, watching a movie, or spending an afternoon by the sea together feels like plenty. At its core the bond is about understanding and acceptance, and it is easy to make sacrifices for each other. That tenderness is precious, but when boundaries blur, whoever is tired or hurt needs to say so, rather than leaving the other to guess. |
The composite Sun sign is not necessarily either person’s Sun sign: in our calculations, only about 25% of pairs have a composite Sun in the same sign as one of their own Suns. When both people share a Sun sign, the composite Sun is always in that sign too (all 169 such pairs in our sample).
The composite Sun in the twelve houses
| Composite Sun in | What this house covers | Share of random pairs |
|---|---|---|
| 1st house | Self, appearance, first impressions | 9.2% |
| 2nd house | Money, resources, values | 8% |
| 3rd house | Communication, learning, siblings, short trips | 8.5% |
| 4th house | Home, roots, inner security | 8.1% |
| 5th house | Romance, creativity, play, children | 8% |
| 6th house | Daily work, habits, service | 8.9% |
| 7th house | Partners, collaboration, one-to-one relationships | 9.1% |
| 8th house | Shared resources, intimacy, transformation | 8.2% |
| 9th house | Travel, beliefs, higher education | 8.5% |
| 10th house | Career, public standing, life goals | 7.5% |
| 11th house | Friends, community, hopes | 8.3% |
| 12th house | The unconscious, solitude, hidden matters | 7.7% |
Houses are derived from the composite Midheaven. Each house comes up close to one time in twelve, with none especially common. The calculator shows what each house means in a composite chart based on your result.
Three oddities of composite charts (our own calculations)
2,100 random pairs of charts of people born in Taipei between 1960 and 2005, calculated by our engine.
1. Mercury and Venus wander too far. In the real sky, Mercury is never more than about 28° from the Sun and Venus about 47°. But a composite takes each planet’s midpoint separately, so if the two people’s Mercuries and Suns lean in different directions, the composite Mercury can end up far from the composite Sun, even on the opposite side. When that happens, read Mercury and Venus mainly by sign and put less weight on their relationship to the Sun.
2. Planets that face each other. If the two people have the same planet almost exactly opposite on the zodiac, the two possible midpoints (one on each side) are nearly equally far, and which one counts as the near midpoint comes down to a degree or two; a slight change in birth time or date can flip it into the opposite sign. In our calculations the most common are Mars (6.2%), Sun (6.1%), Mercury (6%); Neptune and Pluto move so slowly that two people of similar age never have them opposite.
3. The Ascendant is very sensitive. The composite Ascendant is set by the two Midheavens, so a small change in either birth time moves it. In our calculations, if one person’s birth time is an hour later, the composite Ascendant moves 13.7° on average. If one person has no birth time, you can only read the planets’ signs and aspects; the composite Moon is then uncertain by about ±3°, and in about 11.4% of cases that is enough to change its sign.
A real example: Charles and Diana
Using their published birth times: Charles has the Sun in Scorpio and Diana in Cancer, yet their composite Sun lands in Virgo, in the 6th house: a relationship centered on duty, the daily division of labor and “getting things done right”, which fits the official character of that marriage closely. The composite Moon is in Pisces, in the 12th house: feelings kept behind the scenes and hard to put into words. The composite has no Sun–Moon aspect, and Sun–Saturn is a soft sextile: the frame of the relationship is steady, but the two people’s goals and feelings go their separate ways.
The example also shows the Ascendant problem: the Ascendant derived from the composite Midheaven is in Taurus, but the plain midpoint of their two Ascendants is in Libra. Both were born in England (51°–53° north), and the higher the latitude, the further apart the two methods can drift.
A straight word: a composite chart is a way of reading, not the ending of your story
A composite chart merges two birth charts into one “chart of the relationship”, giving you a language for talking about what the relationship itself is like. But it is a mathematical construction, not a sky that ever existed: in our calculations, about 13.7% of pairs get a Mercury or Venus position the real sky could never produce, and about 33% have at least one planet whose midpoint is very unstable. It is a good way to understand how the two of you get along, but it cannot make decisions for you. Everything on this site is for reference and entertainment only.
See the same relationship through another system
BaZi compatibility looks at how two people’s favorable elements and day pillars complement each other, a different angle from the composite chart.
Composite chart FAQ
Which is more accurate, a composite chart or synastry?
They answer different questions. Synastry looks at how two people act on each other: your Venus touching my Mars. A composite chart looks at the personality of the relationship once the two are combined. Reading both gives the fullest picture, and we offer both calculators; see the synastry chart.
Does a composite chart need both birth times?
Ideally. Without birth times you can still calculate the midpoints and aspects of all ten planets, but not the Ascendant or houses; the composite Moon is uncertain by about ±3°, which in our calculations changes its sign about 11.4% of the time. The calculator marks anything that is uncertain.
My composite Mercury is far from the Sun. Is the calculation wrong?
No, it is a feature of the midpoint method. Each planet’s midpoint is taken separately, so Mercury and Venus can end up further from the composite Sun than they ever could in the real sky. In our calculations this happens in about 13.7% of pairs; just read them mainly by sign.
Can I use a composite chart for friends, family or business partners?
Yes. A composite chart describes the relationship between two people, not only romantic ones. For a business partnership, a composite Sun in the 10th or 2nd house and the position of Saturn are worth a closer look; for family, people often look at the 4th house and the Moon.
Why is my composite Ascendant different from other calculators online?
There are two ways to find it: derive it from the composite Midheaven (our method and most software's), or take the plain midpoint of the two Ascendants. In our calculations the two land in the same sign about 83.8% of the time; otherwise they differ, and the calculator lists both. The “time-space midpoint” (Davison) chart is a completely different method again.