Free Synastry Chart Calculator

What does a synastry chart show?

A synastry chart compares the planets in one person’s birth chart with those in another. It can help you explore how you communicate, show affection, approach conflict and respond to responsibility. It describes an astrological pattern between two people, not a verdict on whether they belong together.

This calculator compares the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn, plus each Ascendant when a birth time is known. The inner ring is Person 1 and the outer ring is Person 2. The tables list exact zodiac positions and the angular distance from each listed aspect.

How to read your compatibility result

Start with the closest aspects

A smaller orb means an aspect is closer to its exact angle. Look at the first few contacts before treating every line as equally important. A close Mercury contact can open a question about communication; a Saturn contact can open a question about duties, expectations or long-term commitment.

Connect the chart with what actually happens

For each contact, ask for a concrete example. How do you handle disagreements? Who starts a difficult conversation? Do you agree about time, money and family responsibilities? The usefulness of the interpretation comes from that connection with your experience.

Use the same tool for different relationships

Synastry can be explored for romantic partners, friends and colleagues. The aspects stay the same; the questions you bring to them change. A work relationship calls for discussion of roles, deadlines and accountability rather than assumptions about romantic attraction.

Which aspects does the calculator include?

The calculator uses five major aspects: conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°). Allowed orbs average the two points’ settings: 8° for the Sun and Moon, 6° for the other planets and 5° for the Ascendant. Every match shows its actual orb so you can inspect the calculation.

Harmonious aspects do not remove the need for communication, and challenging aspects do not decide whether a relationship will end. This result includes planetary contacts and positions; it does not calculate a composite chart or give a percentage compatibility score.

Take your question further

Once you have the chart, you can ask about a situation: repeated arguments, an uncertain relationship or a possible collaboration. Add what is happening in real life. To keep a relationship in your account for later readings, use saved compatibility.

Frequently asked questions

Is this synastry chart calculator free?

Yes. The two-ring chart, classical planetary positions and major cross-chart aspects are free and do not require an account. Saved relationship records and further readings use the account experience.

Do I need both birth times?

Exact times allow Ascendants and houses to be calculated. If a time is unknown, select the checkbox. For that person, this tool uses a noon estimate for the slower planets and omits the Moon, Ascendant and houses.

Is synastry the same as a composite chart?

No. Synastry compares two separate birth charts. A composite chart calculates midpoint positions to form a different relationship chart. This tool calculates synastry.

Can synastry predict marriage or divorce?

It cannot reliably predict whether you will marry or separate. It offers a way to discuss relationship patterns alongside your experiences, needs and the other person’s choices.

Are both sets of birth details saved?

This public calculator sends the entered details to Moira’s calculation service and displays the result in this tab. It does not create a saved relationship record or a user profile. See the Privacy Policy for service data handling.