Birth Chart Compatibility Calculator
Compare two birth charts · full 3D synastry aspects · relationship reading
Compare two birth charts using both birth dates, places and recorded times when known. See synastry contacts and a written relationship reading. Sign in to generate a report; free accounts have a monthly allowance.
Start with a calculated aspect list, without signing in. For an AI-written relationship reading and saved report, use the form below; sign-in and your account allowance apply.
Synastry compares one person’s planets with the other person’s. This page brings the chart contacts, a summary score and an AI-written relationship reading together. Choose partner, friend, family member or coworker so the reading addresses the relationship you want to explore.
Read the contact names before the score. A Moon–Mercury contact and a Venus–Mars contact raise different interpretive questions: how you talk about feelings, for example, versus how you express affection and desire. The score condenses the app’s aspect weights; it is not a percentage chance of a relationship lasting.
Keep the direction of each contact clear. “Your Moon with their Mercury” is a different pair of placements from “their Moon with your Mercury.” One can appear without the other. Read the names and planets on each entry before assuming the interpretation applies equally in both directions.
Add recorded birth times when you have them. Without them, Rising signs and house overlays are unreliable, and a Moon near a sign boundary may be uncertain. If another report differs, compare the birth inputs, selected planets, orbs and aspect method. Natal Echo measures angular separation in 3D, which can differ from longitude-only calculations.
Sign in to generate and save the full report. Free accounts receive three reports per calendar month; the form shows your remaining allowance. For a quick aspect list without an account, use the synastry preview linked below. The Moon, Venus–Mars and composite tools each cover a narrower question.
How to Use the Birth Chart Compatibility Calculator
Compare two natal charts in three steps. Birth times add detail; leave an unknown time blank rather than guessing.
- 1. Enter the first person’s name, birth date and birth city. Add the recorded local birth time when known, or use the unknown-time option.
- 2. Enter the second person’s details and choose the relationship type: partner, crush, friend, family or coworker.
- 3. Sign in to generate and save the report, within your account allowance. Read the chart, aspect summary and interpretation together; treat time-dependent placements cautiously when a birth time is unknown.
Compatibility guides
- How to Read a Synastry Chart
- Synastry Aspects Calculator
- Moon Sign Compatibility Calculator
- Venus and Mars Compatibility
- Zodiac Compatibility: Every Sign Pairing
- Free Birth Chart Calculator
- Composite Chart Calculator: A Different Relationship Chart
- Chart Calculation Methodology
- Why 2D and 3D Aspect Angles Differ
Compatibility FAQ
Is this a free birth chart compatibility calculator?
A non-premium account can generate up to three free compatibility reports per calendar month. Sign in first so the reading can be generated and saved. Your remaining allowance appears on the form; premium account terms are separate.
What birth details do I need for a synastry chart?
Enter a name, birth date and birth city for each person. Add the recorded local birth time when you know it. Birthplace matters for time-zone handling and chart location; do not substitute your current city for your birth city.
Can I compare birth charts without birth times?
Yes, you can submit birth dates and places with unknown times. Treat that as a limited comparison: Rising signs and house overlays need reliable times, while the Moon and any planet near a sign boundary can be uncertain. An unknown-time result does not establish that every placement stays unchanged for the entire birth day.
What does the compatibility score mean?
It summarizes the aspects using this app’s scoring rules. Read it alongside the named contacts and interpretation, rather than as a pass or fail. A high score does not establish attraction, consent or safety, and a low score does not decide whether two people should stay together.
How accurate is an astrological compatibility test?
Recorded times improve the chart calculation, especially the Moon, angles and houses. That does not validate a prediction about a relationship. Use the reading to start a conversation, then judge the relationship by communication, choices and behavior.
What is Moon sign compatibility?
It is an astrological comparison of the two Moon placements, often interpreted in terms of emotional needs and comfort. Consider the actual degrees, aspects and both charts rather than assuming one sign pairing guarantees harmony. Unknown birth times can make Moon placements uncertain.
What is the difference between synastry and a composite chart?
Synastry compares positions from two individual birth charts. A midpoint composite constructs a separate chart from corresponding positions in the pair. They ask different interpretive questions; neither proves that a couple is destined to be together. Use the linked composite-chart tool for that separate method.
Why do compatibility calculators give different results?
Check the birth date, local time, city, daylight-saving treatment and unknown-time setting. Calculators can also differ in zodiac convention, aspect angles, orbs, included points and score formulas. Match the inputs and methodology before comparing the summaries.
Should I use the synastry preview or the full compatibility report?
Use the free preview for a calculated aspect list without signing in. Use this page when you want the written comparison and saved report, which require sign-in and use your account allowance. The preview and report can use different selection and scoring rules, so do not expect identical numbers.