◎ Free Composite Chart Calculator
Umbriel's free composite calculator builds the midpoint chart of two people — a single chart for the relationship itself rather than a comparison of two. Free, in your browser, and it shows you the Davison chart beside it because the two disagree in a way worth seeing.
- What you'll needBirth date, time and place for both people
- What you getThe composite midpoint chart, its angles, its aspects — and the Davison chart alongside for comparison
- CostFree — no account required
Runs in your browser. Nothing to install, nothing to set up.
What it actually is
A composite chart is made by taking the midpoint between each pair of planets: your Sun and their Sun produce one composite Sun, and so on for every body. The result is a chart for the relationship as a third thing, rather than a comparison of two separate charts.
It is not a real moment in time. Nobody was born under the composite chart and no sky ever looked like it — it is a constructed object, and the honest way to read it is as a picture of a dynamic rather than as a nativity.
The Davison chart takes a different route to the same question: it is the real chart for the midpoint in time and space between two births — an actual moment, at an actual place. Umbriel computes both, because where they agree is more interesting than either alone.
⚠️ And where they agree is often arithmetic rather than meaning. For the slow outer planets the two methods produce almost the same answer for any two people — a composite and Davison Pluto within half a degree of each other is not a finding about a relationship. Umbriel flags the outer-planet agreement rather than presenting it as a discovery.
How Umbriel computes it
Each composite planet is the midpoint of the corresponding pair, taken on the shorter arc between them — which matters, because the naive average of two longitudes gives the wrong answer whenever the pair straddles 0° Aries. The composite Midheaven is derived from both people's Midheaven values and the houses are built from it, which is why both birth times are required for the angles. The Davison chart is computed separately as a genuine chart for the midpoint moment and the midpoint location, so the two are independent calculations rather than one derived from the other.
What's in your result
- The composite midpoint chartEvery planet as the midpoint of the corresponding pair, drawn as a wheel.
- Composite angles and housesComputed from the midpoint of the two Midheavens, with both people's birth times required.
- Composite aspectsThe internal structure of the relationship chart.
- The Davison chart alongsideThe real chart for the midpoint moment and place, for comparison.
- Where the two agree and where they do notWith the outer-planet agreement flagged as the arithmetic it usually is.
Common questions
What is a composite chart?
A chart built from the midpoints between two people's planets, read as a chart for the relationship itself rather than for either person.
What is the difference between a composite and a Davison chart?
A composite is a mathematical midpoint chart for no particular moment. A Davison is the real chart for the midpoint in time and space between the two births — an actual sky. Umbriel computes both.
Do both people need a birth time?
For the planets, no. For the composite angles and houses, yes — both times, since the composite Midheaven comes from both.
Why do the composite and Davison charts agree on the outer planets?
Because the outer planets move so slowly that both methods land in nearly the same place for almost any two people. It is a property of the arithmetic, not a statement about the relationship, and Umbriel says so.
Can you have a composite chart with someone you are not in a relationship with?
Yes — the calculation makes no assumption about the kind of relationship. Composites are used for business partners, siblings, bands and co-authors as readily as for couples, and the chart does not know which it is looking at.
Is the composite chart calculator free?
Yes — composite, Davison and the comparison between them, with no account.
Go deeper
Each of these is a free tool in its own right.
Umbriel offers every system here as a set of prompts to think with, never as a statement of fact about who you are. Take what's useful, leave the rest.