Relationship compatibility: how to read synastry

Check permission and birth details first

Before opening two charts, ask whether the other person actually wants to take part. A birth date, time and place are personal details. Ask separately before sharing a screenshot. Silence does not mean someone agrees to have their information uploaded or their reading sent to a group chat. A respectful reading begins before the calculations do.

For each person, label the time as recorded, approximate or unknown. Filling an unknown time with a guess introduces false precision, especially into house comparisons. If your time comes from a record and theirs comes from a family recollection, say so at the beginning. Two completed forms do not necessarily represent equally reliable information.

Distinguish synastry from a composite chart

Synastry is a traditional interpretive framework for relationships between two charts. A composite chart is a different technique; grouping them under relationship astrology does not make their calculations identical. When choosing a lesson or a paid reading, check which method is being used. Knowing the question you want to explore helps you choose the appropriate introduction.

Try not to turn ‘Do our Sun signs get along?’ directly into a relationship decision. How you speak to one another, respect boundaries and negotiate expectations can be discussed in ordinary life. A chart can accompany that conversation. It cannot replace listening to what the other person actually says, including when their experience does not match an interpretation.

Source: Astrodienst: the synastry concept

Read relationship compatibility through six questions

Love: Sun, Moon and Venus contacts can prompt reflection on appreciation and affection. Ask each person which actions help them feel loved. Similar ways of showing affection do not mean you share the same needs in every part of the relationship.

Emotional bond: Read Moon contacts alongside what you need after a difficult day. One person might want company while the other needs some time alone. A Moon–Saturn interpretation can open a conversation about boundaries and responsibility; it does not establish that somebody is cold or unfeeling.

Chemistry: Venus–Mars contacts are traditionally associated with attraction and initiative. Only conversation can establish whether interest is mutual and the pace feels comfortable for both people. A strong chart contact is not evidence of consent, respect or a shared wish to stay together.

Communication: Connect Mercury interpretations to a specific conversation habit. One person might look for a quick solution while the other wants to be understood first. ‘Do I want listening or suggestions right now?’ gives a Mercury–Moon or Mercury–Saturn reading something concrete to explore. The chart cannot answer on your behalf.

Commitment: Saturn, Jupiter and seventh-house contacts, where reliable birth times support them, can accompany a discussion of long-term expectations. Explain what you want around living together, finances and personal space. A Saturn contact guarantees neither marriage nor a burdensome relationship.

Intensity: Pluto, lunar nodes and supported house overlays may open symbolic questions about why a connection occupies your thoughts. Intensity is not relationship quality. Do not excuse jealousy, control or crossed boundaries as a ‘karmic bond’; evaluate the actual behavior.

Read an aspect list in context

An aspect list describes angular relationships between planets; an interpretation gives those relationships a meaning. First identify the two planets being compared and how close the contact is. Do not find the word ‘square’ or ‘trine’ and turn it into a verdict on the whole relationship. The allowed distance from an exact aspect can also differ between methods or apps.

While learning, avoid trying to solve every placement in one session. Choose a contact, write its traditional interpretation in your own words and consider a concrete question it could prompt. If the reading mentions communication tension, ask ‘Can we hear each other out during a disagreement?’ The answer comes from your experience and conversation, not from the chart itself.

Birth chart compatibility: a worked 2° orb example

Use two hypothetical placements to understand the calculation: Person A’s Moon at 10° Taurus and Person B’s Venus at 12° Taurus. Their zodiac longitudes are 40° and 42°. The shortest angular separation is 2°, so this is a Moon–Venus conjunction with a 2° orb from exact alignment. The orb is an angular distance, not a relationship success percentage. These placements are not a real customer’s chart or today’s sky.

When reading the Moon as emotional needs and Venus as a way of expressing affection, hear both people’s experiences. A might prefer quiet after a hard day, while B sees spending time together as support. The chart does not decide whose preference is right. ‘What kind of attention would help you on a day like that?’ gives both people a way to compare the interpretation with actual experience.

Baby Astro considers love, chemistry, emotional bond, communication, commitment and intensity separately. Intensity is not relationship quality. Do not turn this single Moon–Venus contact into the same score for every theme. Look for repeated themes in other planetary contacts and, when times are known, house overlays in both directions. Writing the same aspect in reverse does not add another independent indicator.

Without a birth time, the Moon’s exact degree may also be uncertain. Avoid definite Ascendant and house readings, including claims about the other person’s planets in those houses. Marking an unknown time in the free preview is a better starting point than adapting this example’s exact degrees to your own chart.

Check house overlays in both directions

A house overlay describes where one person's planet falls in the other person's houses. Placing only A's planets in B's houses covers one direction. Examine B's planets in A's houses too. If the owner of a set of houses has no reliable birth time, omit that direction's house interpretation; the other person's known-time houses may still be considered separately.

In a hypothetical teaching example, A's Venus falls in B's seventh house while B's Venus falls in A's eleventh. These are not the same placement written twice. They can prompt separate questions about partnership expectations for B and friendship or shared aims for A. Do not assume your relationship has these placements without a calculation. The example predicts neither a marriage nor a friendship outcome.

Look for independent indicators when discussing repeated themes. Listing the same Moon–Venus aspect once as A–B and again as B–A does not create two pieces of evidence. Another planetary contact or a reliable house overlay may raise a similar question. Even several similar interpretations do not prove that the theme occurs in your actual relationship.

Make a shared conversation note instead of a score

Create three short fields: the topic we want to discuss, our observations and a behavior to try. One person might want a quick reply while the other needs time to think. Rather than assigning this difference to a sign, discuss a response window that works for both. Trying it for a week and revisiting it gives you something more concrete than the label ‘incompatible’.

Agreement is not a requirement of this exercise. If an interpretation fits you but not the other person, do not try to correct their experience. They can also decide to stop discussing astrology. Trust, respect and consent need to be evaluated through behavior; they are not conclusions a planetary contact establishes on someone's behalf.

If you are considering a paid synastry reading, ask about scope before length. What information will be used? What will be left uninterpreted if a birth time is missing? Are the limits explained clearly? Showing a number as a percentage does not make it the probability that your relationship will succeed. Definite marriage, breakup or soulmate claims are poor reasons to purchase.

You can return to Baby Astro's synastry guide for the basic terminology, then explore a comparison at your own pace. This article is intended to clarify the questions you ask during a reading, not collect more personal details or pass judgment on your relationship. End your note with a small behavior you can work on together rather than a prediction you feel obliged to fulfill.

Common questions