Why Compatibility Scores Are the Wrong Question

By Galaxia · Updated Sep 30, 2026 · 6 min read

Galaxia describes what a chart shows, not what will happen. How we write about astrology →

A compatibility score works like this: you enter two signs, the algorithm compares how those types tend to get along, and you get a number. Some versions are more sophisticated, adding Moon signs or rising signs to the calculation. The premise remains the same. You get a grade.

The problem is that the grade is answering a question about categories rather than about you. There are twelve Sun signs. A calculator that tells you Aries and Scorpio have 60% compatibility is making a statistical claim about twelve categories of people, which is to say it is saying something about roughly 700 million individuals based on one fact about each of them. The claim is almost empty by the time it reaches you.

This is also why you have almost certainly known couples who should not work by any compatibility metric and do, and couples who check every box and do not. The score is about the types. The people are not the types.

What synastry actually does

Synastry is a comparison of two complete charts, not two Sun signs, with every placement and every contact between them. What you are reading is not a grade but a map: here is where your tendencies run parallel to theirs, here is where they run perpendicular, here is where your Saturn lands on their Moon and what that generates, here is where their Venus touches your Jupiter and why some things between you have always felt easy without either of you knowing why.

This is not a compatibility score. It is a description of the terrain. And knowing the terrain is more useful than a grade because the terrain tells you what to expect and where the work is, rather than whether to proceed at all.

What a synastry chart actually tells you is the method: flows and catches, and why the easy parts deserve to be named first. Seven synastry aspects that shape how a relationship feels is the close reading of specific contacts. This post is about why the number was the wrong object in the first place.

The things that actually predict whether a relationship works

How two people handle conflict is more predictive of long-term outcomes than any compatibility percentage. The chart shows this through Mars: both people’s Mars placements describe how each one handles friction, and the contacts between those Mars positions describe what happens when the two friction styles meet in the same room.

Two people with Mars in Libra both tend to avoid direct conflict. In one scenario, this means small things never get addressed until they are large. In another, it means two people who are both diplomatic and both willing to find common ground. Context and choice shape which version you get. The chart tells you the tendencies. It does not decide the outcome.

Mars in Aries and Mars in Capricorn in the same relationship often means quick, hot conflict that resolves fast on one side and controlled, strategic friction that resolves slowly on the other. Neither is better. They are different engines that need different approaches to keep from frustrating each other.

None of this is a score. It is two descriptions that you can actually use.

The Moon contacts

How two people process emotional need is the other major factor, and it lives in the Moon contacts. The aspects between two moons tell you whether emotional life in the relationship feels like a shared language or a translation problem. Moon conjunct Moon or Moon trine Moon tends to mean people who understand each other’s emotional responses without much effort. Moon square Moon tends to mean they are in friction there, and the friction is often the kind where both people are responding to something real but not quite to the same thing.

This does not make Moon square Moon relationships unworkable. It means they require more translation than Moon trine Moon relationships, and knowing that is more useful than being surprised by it.

If one Moon is also square the other person’s Saturn, the translation problem has a harder edge. That contact has its own family reading, and it shows up in partnerships too. The point here is the same: name the contact. Do not average it into a percentage.

Sun contacts and recognition

The aspects between two suns describe recognition: whether each person sees the other clearly, whether they feel seen in return, whether they are in some sense oriented toward the same things. Strong Sun contacts tend to produce relationships where each person feels the other is fundamentally comprehensible. Weak or challenging Sun contacts tend to produce relationships where people feel slightly opaque to each other, where they like each other but cannot quite explain why or what the other person is doing in a given moment.

Neither configuration is automatically good or bad. Relationships between people who are too similar can lack the kind of difference that produces growth. Relationships between people who cannot quite read each other can be interesting and friction-generating in ways that lead somewhere. The map tells you what you are working with. It does not tell you what to do with it.

A Sun-sign compatibility table cannot see any of this. Two Leos can have a trine between their moons and a square between their Mars placements, or the reverse, and those two relationships will not feel like each other. Your Sun sign is not your personality for one person. It is even less of a relationship.

What “compatible” usually means and what you probably want

In most compatibility frameworks, compatible means similar. Similar enough that less translation is required, that fewer things need to be worked out, that the baseline is easier. And low-friction is genuinely valuable. But friction is not the same as incompatibility, and that distinction matters.

Most people do not actually want the absence of friction. They want friction they can navigate. They want to know where the hard parts are and why, so that when those parts surface it feels like information rather than evidence that something is fundamentally wrong. That is the question synastry can actually answer.

Not: are we compatible? But: what does this look like between us, and where do we have to work harder than average? The second question is more honest and more useful. It is also the question the chart is actually built to answer.

Galaxia will not answer the first question for you. A birth chart does not decide a life, and a synastry chart does not decide a relationship. How Galaxia handles astrology. What a chart cannot tell you is the longer list. “Will this work” belongs on it.

On the six dynamics that define a relationship

The most revealing contacts in a synastry are the ones between Mars and Mars, Moon and Moon, Sun and Sun, Venus and Venus, and the significant cross-aspects: one person’s Saturn to the other’s personal planets, one person’s Moon to the other’s Venus, the contacts that describe how care gets expressed and whether it lands.

None of these produce a score you should trust as a verdict. Together, they produce a picture of two specific people and how their habits interact in practice. That picture is worth more than any percentage, because percentages average out exactly the details that matter.

The free comparison shows you the contacts between two full birth charts with plain descriptions of each one. Flows, catches, and the terrain between two people. Vela can walk a specific contact without inventing a grade. Not a substitute for the two of you. A map of where the terrain is going to ask something of you.