Zodiux.

Are we compatible?

Put in both charts and get the real read — what clicks, where it grinds, and what to actually do about it.

Two luminous spheres tracing overlapping orbital paths — representing two birth charts meeting in synastry

You

Optional — adds rising sign & sharper results.

Them

Optional. Without both birth times the Moon contacts and the angles are left out.

Know your own chart first

Compatibility makes more sense once you've seen your own sky. Run your full birth chart in a tap.

Calculate my birth chart

What this calculator actually does

Most "compatibility" tools compare two sun signs and stop. This one does not. When you enter both birth dates — and, ideally, both birth times and cities — it computes two complete birth charts in your browser, then looks at the angles between your planets and theirs. That comparison is called synastry, and it is the technique real astrologers use.

Concretely: it measures the separation between every pair of planets across the two charts and keeps the ones that land within a defined tolerance of a classical angle — conjunction (0°, 7° orb), sextile (60°, 5°), square (90°, 6°), trine (120°, 7°) and opposition (180°, 7°). Each contact it finds is assigned to one of four dimensions and weighted: a Sun–Moon contact carries far more than a Jupiter–Neptune one. The four dimension scores start at a neutral 50, move with the contacts found, take a final adjustment for how the two charts' elemental balances sit together, and are clamped to the 6–97 band. The headline figure is those four weighted — chemistry heaviest, staying power lightest.

The result tells you how many cross-aspects it found, and names them. If it says nine, it looked at every planet pair in both charts and nine of them were close enough to a real angle to count. Nothing about the number is decorative.

Why birth times change the answer here

Birth time is optional in the form, and the tool works without it — but it works differently, and it says so. Without a time, both charts are computed for local noon. The Sun and the outer planets barely move in a day, so those contacts stand. The Moon can travel up to about 15° in 24 hours, which is wider than every orb in the list, so a Moon contact found from a noon-assumed chart may not be real. The rising signs are omitted entirely rather than guessed, which removes the angles from the comparison altogether.

In practice: two birth dates give you a solid read on the slower, structural contacts. Two birth times give you the Moon and the angles, which is where most of the emotional texture of a synastry reading lives. How much a wrong birth time actually costs you goes through this properly.

Where it stops

A synastry score describes the geometry between two charts. It does not know how long you have known each other, whether either of you wants the same thing, how you were each raised, or whether the relationship is good for you. Two charts with an excellent score belong to people who may be entirely wrong for each other, and a difficult score describes friction, not doom — plenty of durable relationships run on squares.

Treat the output as vocabulary. "Your Mars squares their Saturn" is a useful name for a pattern you have probably already noticed; it is not a prediction and it is not a verdict. No compatibility tool should decide a relationship, and this one is explicitly built for reflection and entertainment rather than advice. Synastry, explained properly covers what the technique can and cannot support.

Sun-sign pages, and how they differ from this

Below are all 78 sun-sign pairings, each with its own page. Those pages use a completely different and much simpler model — element, modality and the angle between the two signs — because a sun-sign pairing fixes nothing else. Every couple sharing those two signs gets the same number. The full model is published, tables and arithmetic included.

They are worth reading for the language, not the verdict. The calculator above is the one that looks at two actual people.

Common questions
Do I need both birth times?

No, and the tool runs without them. With both times you also get the Moon contacts and the angles, which is where most of the emotional detail of a synastry reading sits. Without them, both charts are computed for local noon and the rising signs are left out rather than guessed.

Is this the same as the sun-sign compatibility pages?

No. The sun-sign pages score a pairing of two signs from element, modality and the angle between them — the same number for everyone with those signs. This calculator compares two whole charts and finds the actual cross-aspects between them, so no two couples get the same result.

Does my partner's birth data get sent anywhere?

No. Both charts are computed in your browser and the birth details are never transmitted to Zodiux. They are not written into the page address either, so they do not end up in your history or in a link you share by accident. What is stored, and how to clear it covers the detail.

What counts as a good score?

Nothing here is a pass mark. The scale is clamped to 6–97 precisely so no pairing reads as hopeless or guaranteed. A high number means the two charts have a lot of easy contacts; it says nothing about whether either person is kind, available or interested. Read the named aspects rather than the headline.

Charts and cross-aspects are computed in your browser with the open-source Astronomy Engine, using the tropical zodiac — the full method is published. Written and reviewed by the Zodiux editorial team · Last reviewed · Editorial standards and corrections · For reflection and entertainment, not advice.