Synastry calculator
Two birth charts, the aspects between them and both wheels drawn as one. The mechanics of a comparison, computed rather than interpreted.
Which contacts astrologers look at first
Sun to Moon between two charts is the classic one: one person's sense of purpose meeting the other's sense of safety. It tends to describe couples who feel domestically easy with each other whatever else is going on.
Venus to Mars is the attraction contact, and it is as loud as its reputation. Saturn to anything is the one that decides whether a thing lasts: it is heavy and it commits, and people either describe it as steadying or as being sat on, often both in the same decade.
A count of harmonious against tense aspects is the least useful number on the page, which is why it is the smallest thing on it. Relationships with no friction in the charts are frequently the ones that quietly end.
Questions
What is synastry?+
Laying one birth chart over another and reading the angles between them. Where a planet of yours meets a planet of theirs, astrologers read a place the two of you affect each other — comfortably at some angles, abrasively at others.
Do more harmonious aspects mean a better relationship?+
No, and this is the thing the counts are most often misread as. Charts with almost nothing tense between them tend to describe couples who get on and drift apart; the friction aspects are usually what holds attention. What matters is which planets are involved, not the ratio.
Does this work for people who are not a couple?+
Yes. Synastry is a comparison of two charts, and the pair can be a parent and a child, two colleagues, siblings or friends. What changes is which contacts you care about.
What is a bi-wheel?+
Two charts drawn on one diagram, one inside the other, so you can see where the outer person's planets land in the inner person's houses. It is the quickest way to see which areas of one life the other person keeps turning up in.
Do we both need birth times?+
Not for the aspects between planets, which are what the table shows. Houses need times, so without them you can see that a Venus meets a Mars but not which part of life it lands in.
What it means between you two
This page counts the aspects. The compatibility reading takes the same two charts and writes what they do to each other: what draws you together, what you keep arguing about, and what each of you is actually asking for.
Read our compatibility