Big Three Compatibility Guide

Person A has a Leo Sun, Virgo Moon and Libra rising; Person B has a Pisces Sun, Taurus Moon and Capricorn rising, giving contrasting Suns, two earth Moons and two cardinal Rising signs.

The Big Three are the Sun sign, the Moon sign and the Rising sign. The Sun describes identity and purpose, the Moon describes emotional habits and what helps a person feel settled, and the Rising sign, also called the Ascendant, describes outward approach and first impressions.

Comparing all three across two people gives a much fuller picture than Sun signs alone. You are asking three questions: do these two people aim at similar things, do they need similar things, and do they come across in compatible ways?

The Sun sign needs only the birth date. The Moon sign needs the date and, on days when the Moon changes sign, the time too: the Moon covers about 13 degrees a day, so it spends only about 2.3 days in a sign on average. The Rising sign needs an exact birth time and place.

The Ascendant moves about 1 degree every 4 minutes. A birth time that is 30 minutes off shifts it about 7.5 degrees, and one that is 2 hours off is likely to give a different sign altogether. If either person lacks a birth time, compare Sun and Moon only and treat the Rising layer as unknown.

Compare each of your three placements with each of the other person’s, which gives nine pairings. The grid shows what each one tends to tell you.

Work through these steps and stop when you have a few clear points.

1. Write both people’s three signs side by side.
2. Note which pairings share an element, which share a modality and which are neither. You only need to mark likenesses and contrasts here, not score them.
3. Mark the three pairings that seem to matter most to the two of you, usually Moon with Moon, your Sun with their Moon and their Sun with your Moon.
4. Turn each into a question. Ask not whether the match is good but what each likeness makes easy and what each contrast asks of you both.

Take two made-up people. Person A has Sun in Leo, Moon in Virgo and Libra rising. Person B has Sun in Pisces, Moon in Taurus and Capricorn rising.

Their Suns are Leo (fire) and Pisces (water), a contrast between a showy, warm style and a gentle, absorbent one. Their Moons are Virgo and Taurus, both earth, a likeness that suggests comfort in practical routines and quiet evenings. Their Rising signs are Libra (air) and Capricorn (earth), both cardinal, so both start things and look after appearances, but one is gracious and the other reserved.

So the picture is a contrast in purpose, a shared way of settling and a similar tempo with a different tone. The useful conversation might be about how each person likes to be seen and how they unwind, rather than whether the two are compatible.

Not every cell in the grid weighs the same. Moon with Moon is usually read as the most telling for daily life, because it shows what each person does when tired, upset or at home. Sun with Moon is the classic pairing in the tradition, because it joins what a person is aiming at with what the other person needs.

Sun with Sun and Rising with Rising are read more lightly. They describe overall direction and social style, which matter for shared plans and for how the two of you look to other people. If you only have time for three cells, take Moon with Moon, your Sun with their Moon and their Sun with your Moon.

Read the grid in terms of likeness and contrast, not good and bad. Two Moons in the same element may understand each other quickly and also fall into the same blind spot. Two Moons in contrasting elements may misread each other and also teach each other something new.

These three placements leave out communication, which is Mercury, values and affection, which are Venus, and drive, which is Mars. They also leave out the aspects between two charts, the houses and everything about how the two people actually behave with each other.

Treat the comparison as a way to begin a conversation. If you want to go further, add the other personal planets or compare the two charts in full, and always weigh what you see in the relationship above what you see in the chart.

The first example assumed every placement was clear. This one shows a boundary case that catches many people. Take a made-up person, Dana, born on a day when the Moon stands at 27 degrees of Gemini at midnight. Gemini ends at 30 degrees, so 3 degrees remain. At about 13 degrees a day, the Moon covers them in 3 divided by 13 of a day, or about 5.5 hours. Born before about 5:30 in the morning, Dana has a Gemini Moon. Born after, Dana has a Cancer Moon. The Moon's speed varies from roughly 12 to 15 degrees a day, so the cutoff time is an estimate and a chart calculator gives the exact moment.

Now pair Dana with a partner whose Moon is in Pisces. A Cancer Moon shares the water element, which reads as quick emotional understanding. A Gemini Moon, an air sign, reads as a difference in how feelings get processed, by talking or by feeling. The same birthday gives two different conversations, and only the birth time decides which one applies.

What if we share the same Sun sign? It tells you less than you might think. Two Leo Suns can have Moons in opposite elements and Rising signs far apart, so the grid still has eight other cells to read.

What if my partner will not share a birth time? Respect that and compare Sun and Moon. Do not guess a Rising sign, because a guess only produces a confident-sounding wrong answer.

Can I use the grid for friends, family or coworkers? Yes. The same questions about aims, needs and manner apply to any pair. It is a vocabulary for how two people differ, not a ranking of relationships.

The Big Three leave out communication, affection, drive, chart aspects and, above all, how the two people actually behave with each other.