What are the Big Three in astrology?

Sun, Moon and Rising sign — the three most important points of a birth chart. The Sun describes your core self, the Moon your emotional life, the Rising sign how you come across. Together they say far more about a person than the zodiac sign alone.

Why isn’t the zodiac sign enough for compatibility?

Because your zodiac sign is only the Sun. Two people can have "incompatible" sun signs and still harmonise beautifully — because their Moons understand each other, or their Rising signs strike the same everyday tone. The Big Three comparison shows all three levels.

What if we don’t know a birth time?

Then we compare Sun and Moon — the two inner levels. The Rising sign depends on the exact time and birthplace, because it changes roughly every two hours. Add the times later and the comparison completes itself.

How is the harmony score calculated?

Deterministically, from classic astrology logic: signs of the same element harmonise strongly, fire with air and earth with water complement each other, square configurations create friction. Modality and the geometric relationship of your signs are added on top. Same input, same result — no random generator.

Is a low score a bad sign?

No. A low score means your energies differ and need translation. Those couples often grow more than couples with pure harmony. The score shows how much work the connection carries — not whether it is worth it.

The Astro AcademyBy Theresa

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Astrology · Compatibility

Big Three compatibility
calculator — Sun, Moon and Rising, compared

Your Big Three are the foundation of any birth chart: the Sun (who you are at the core), the Moon (how you feel) and the Rising sign (how you come across). This calculator compares all three levels between you — free, with a harmony score and a clear read per level.

Are you a match?

Compare your two birth charts and see how well you click — in love, everyday life and on a soul level.

Person 1 — you

Nameoptional

Birth date *

Sets the Sun, Moon and every planet.

Timeoptional

Without a time we cannot compute the ascendant or houses.

Birth city

Fixes the exact position of the houses.

Person 2 — your match

Nameoptional

Birth date *

Sets the Sun, Moon and every planet.

Timeoptional

Without a time we cannot compute the ascendant or houses.

Birth city

Fixes the exact position of the houses.

Swiss-Ephemeris accurateNo sign-up neededResult in seconds

The Ascendant needs birth time and birthplace. Without a time we compare Sun and Moon — which is already half the story.

How it works

Three steps to your Big Three comparison

Enter both birth data sets
A date for each of you is required. Time and birthplace unlock the Rising level — without them we compare Sun and Moon, which is already half the story.
Calculate the Big Three
We build both charts from your data with the Swiss Ephemeris engine and read out Sun, Moon and Rising for each of you.
Read it level by level
Each level gets the sign pair, a harmony score and a plain-language read — what pulls, what chafes, where you can grow.

Big Three — frequently asked questions

What are the Big Three in astrology?: Sun, Moon and Rising sign — the three most important points of a birth chart. The Sun describes your core self, the Moon your emotional life, the Rising sign how you come across. Together they say far more about a person than the zodiac sign alone.
Why isn’t the zodiac sign enough for compatibility?: Because your zodiac sign is only the Sun. Two people can have "incompatible" sun signs and still harmonise beautifully — because their Moons understand each other, or their Rising signs strike the same everyday tone. The Big Three comparison shows all three levels.
What if we don’t know a birth time?: Then we compare Sun and Moon — the two inner levels. The Rising sign depends on the exact time and birthplace, because it changes roughly every two hours. Add the times later and the comparison completes itself.
How is the harmony score calculated?: Deterministically, from classic astrology logic: signs of the same element harmonise strongly, fire with air and earth with water complement each other, square configurations create friction. Modality and the geometric relationship of your signs are added on top. Same input, same result — no random generator.
Is a low score a bad sign?: No. A low score means your energies differ and need translation. Those couples often grow more than couples with pure harmony. The score shows how much work the connection carries — not whether it is worth it.

What you get

Three levels, three honest answers

Sun — who you are at the core
Do your basic natures fit? The Sun level shows whether your life directions amplify each other or work against each other — and what you can make of it.
Moon — how you feel
The Moon level is the least visible and often the most important: how do you each handle feelings, and what does each of you need to feel safe? This is where relationships hold or fray.
Rising — how you land on each other
First impressions, the everyday tone, the chemistry in the room: the Rising level shows how you come across to each other day to day — it needs both birth times.
One score per level, clearly derived
Each level gets a 0–100 harmony score — derived from element, modality and how your signs sit relative to each other. No randomness, no black box.