Compatibility: the aspects between two birth charts

Most places explain compatibility by matching just two Sun signs. Synastry, on the other hand, places two people's whole birth charts side by side and calculates the aspects one person's planets make with the other's. The calculator below does this without an account, and it never reduces the result to a single “compatibility percentage.”

What does the calculator show?

• The five major aspects (conjunction, sextile, square, trine, opposition) between the two charts' planets, and each aspect's orb
• A count of aspects by type: harmonious (trine, sextile), tense (square, opposition) and conjunction
• The contacts traditionally looked at first: Sun-Moon, Venus-Mars, Moon-Moon, Venus-Venus and Mercury-Mercury
• The two people's element distribution (across the ten planets)

If a birth time is unknown

If one person's birth time is unknown, the calculation uses noon for that day and that person's Moon aspects aren't factored in: the Moon moves 12 to 15 degrees in a day, so without a time its position isn't precise enough to judge an aspect. The rising sign isn't shown in this case either. The other planets move very little in a single day, so their aspects remain meaningful; only a planet that changes sign that same day (for example, the day the Sun changes sign) is shown with both possible signs.

In the app: three techniques

• Synastry: the aspects one person's planets make with the other's, and how each falls into the other's houses (house overlay).
• Composite: a shared chart built from the midpoints of corresponding points in the two charts.
• Davison: a chart calculated for the exact midpoint in time and place between the two birth moments.

The type of relationship changes the interpretation

When you add a relationship profile in the app, you choose the relationship's type: partner, child, family, friend, business partner, or other. The interpretation is written with this context in mind; a business partnership isn't treated like a romantic relationship.

The person you add stays on record. If you ask for an analysis about the same person months later, you won't need to re-enter their birth details.

Why isn't there a compatibility score?

Reducing the relationship between two people to a single number creates an impression of certainty that doesn't exist. Instead, the aspects, orbs and house overlays are shown in a table; the interpretation is based on that data.

The interpretation doesn't pass judgment on the relationship's future in terms of “it will work” or “it won't.”