Compatibility Check

Reading your compatibility score

What the score actually measures

The number you get is not pulled from a sun-sign table. When you hit Calculate, we compute both birth charts from scratch — real planetary positions for the date, time, and place each of you was born — and compare them five ways. Moon-to-Moon synastry carries the largest share of the final score at 25%, because in my experience it is the best single predictor of whether two people can relax around each other. The sun-sign blend (element plus modality) contributes 20%, Venus-to-Venus another 20%, Mars-to-Mars 15%, and the last 20% comes from every major aspect between your personal planets — Sun, Moon, Mercury, Venus, and Mars — crossed against each other. The exact weights, orbs, and matrices are published on our methodology page.

The sun blend compares elements and modalities. Fire and air feed each other, as do earth and water, and the scoring reflects that: a Leo–Gemini pairing (fire–air) rates higher on this component than Leo–Leo, because two suns in the same element share a rhythm but complementary elements add something the other lacks. Modality matters less but still counts — two fixed signs, say Taurus and Scorpio, lose a few points here, since neither of you backs down first.

The moon comparison looks at the actual angle between your Moons, not just their signs. Moons in trine — 120° apart — score near the top. Moons in square read as friction around comfort and habit: how each of you behaves at home, tired, after a bad week. Venus and Mars are scored the same way, planet against planet. Venus is affection style, Mars is drive and desire, and a tight Venus–Venus square is two different definitions of “romantic” living under one roof.

The aspect grid is where the interesting material hides. We check all 25 pairings between the two charts’ personal planets and score every hit: trines and sextiles lift the number, squares and oppositions pull it down, conjunctions land mildly positive — and each aspect counts for more the closer it sits to exact. A square with a half-degree orb outweighs a lazy 7° trine.

Which inputs actually matter

Birth date and place are required; birth time is optional here. Leave it blank and we assume noon. For the Sun, Venus, and Mars this barely matters — they move a degree a day or less. The Moon is the exception: it covers roughly 13° per day, so a noon guess can be off by up to 6.5°, and if one of you was born on a day the Moon changed signs, the moon component can genuinely land wrong. If a result surprises you, check whether either Moon sits near 0° or 29° of its sign — that is the tell.

Birthplace matters more than people expect, and not for mystical reasons: we use the coordinates to work out the timezone, so the same clock time in Auckland and in Lisbon resolves to very different actual moments — and different planetary positions.

How to read a low score

Any component under 50 shows up flagged as a growth area below your result. Read those as “this is where the translation work is,” not as a verdict. Squares are friction, and friction is also engagement — I know couples a decade in who run almost entirely on Mars squares and would be bored by anything smoother. The pattern I would actually take seriously is a low moon component combined with a low aspect score: comfort styles clash and there is no easy planetary bridge elsewhere, which is the signature behind “we love each other but living together is exhausting.”

The reverse also holds. A middling overall number with one standout — a tight Venus–Mars trine in the aspect list, say — often describes a very specific relationship: not easy, but magnetic.

Common questions

Do we both need exact birth times?

No. The scoring uses planetary longitudes only — never house cusps or the Ascendant — so an unknown time costs you some Moon precision and nothing else.

Is sun-sign compatibility enough on its own?

It is one component of five here for a reason, and weighted below the Moon. Two people with “incompatible” suns and a close Venus–Mars trine will feel more chemistry than “compatible” suns with nothing else going on. The longer argument is in why sun-sign compatibility isn’t enough.

What counts as a good score?

The weighting pulls most pairs into the 45–70 band. Above 75 is genuinely uncommon and usually means harmonious Moons plus several tight trines. Below 40 means the charts mostly square off — read the breakdown before drawing conclusions, because one heavy component can drag a number that is otherwise fine.

Why does another site give us a different number?

Different weights, orbs, and aspect sets — there is no ISO standard for synastry. Ours are documented in full on the methodology page, so at least you can see exactly what you are disagreeing with.

Where does our birth data go?

Nowhere — the charts are computed in your browser. Your own details persist locally so the birth chart and daily transit pages can reuse them; your partner’s details are not kept at all.