Free Synastry Chart & Birth Chart Compatibility

Compare two birth charts · real synastry aspects · relationship reading

Enter two birth charts and this relationship astrology calculator compares them with real synastry — Moon, Venus, Mars, Rising, house overlays and the aspects between both charts — then gives you a compatibility score and a written relationship reading. Free, no sign-up.

Quick answer: this is a free synastry chart calculator. Enter two sets of birth details and it compares both charts — Moon, Venus, Mars, Rising signs, house overlays and the aspects between them — then returns a compatibility score and a written relationship reading. Birth chart compatibility read this way is far more accurate than matching Sun signs alone.

What the score actually uses: your Sun signs for core temperament, Moon-to-Moon contacts for emotional rhythm and how each of you recovers from stress, Venus and Mars for attraction and desire style, Mercury for communication, and Saturn contacts for staying power. Harmonious aspects (trines, sextiles) show where things flow; squares and oppositions show friction that often generates the real growth. House overlays then place each person's planets into the other's life areas.

Relationship astrology calculator: choose the relationship type — partner, crush, friend, family, or coworker — and the reading weighs the same synastry differently, because what makes a good colleague is not what makes a good partner.

Compatibility chart: your compatibility chart is built from both complete birth charts rather than a Sun-sign lookup table. This astrological compatibility test scores emotional, mental, and romantic connection, then explains the strongest links and the friction points worth knowing about.

Synastry chart: synastry overlays one chart onto the other so every planet-to-planet aspect becomes visible — Venus to Mars for attraction, Moon to Moon for emotional rhythm, Saturn contacts for staying power. Birth times sharpen the house overlays; noon works as a fallback when a time is unknown.

Moon sign compatibility: the Moon governs emotional needs, comfort, and how each person recovers from stress, so moon sign matches often predict day-to-day harmony better than Sun signs do. Two charts with 'incompatible' Sun signs routinely score high once their Moons and Venus placements meet.

Compare birth charts: enter both birth dates (plus times and places if you have them) and the calculator compares two complete charts instantly — free, with no sign-up required. Whether you call it an astro compatibility chart, a synastry chart, or simply birth chart compatibility, it is the same technique: two whole charts laid over each other rather than two Sun signs looked up in a table.

How to Compare Natal Charts

Step-by-step guide to comparing two birth charts for relationship compatibility

  1. 1. Enter both birth dates, times, and locations
  2. 2. Get instant synastry analysis with compatibility score
  3. 3. Receive expert astrological insights on your cosmic connection

Compatibility guides

Compatibility FAQ

How accurate is natal chart compatibility?

Our compatibility reports use real synastry—comparing planetary positions between two charts—not generic sun sign matching. Accuracy depends on having correct birth dates, times, and locations for both people.

What is natal chart comparison?

Natal chart comparison (synastry) overlays two birth charts to see how planets interact. Harmonious aspects (trines, sextiles) suggest ease; challenging ones (squares, oppositions) can indicate growth areas. Our tool analyzes these connections.

Can I compare charts without birth time?

Yes. Use 12:00 PM for unknown times. You'll get planetary sign comparisons, but house overlays (which life areas connect) will be less accurate. Birth time improves compatibility detail.

Is synastry the same as compatibility?

Synastry is the astrological technique for comparing two charts. Our compatibility report uses synastry plus AI interpretation to explain how your energies align—strengths, challenges, and guidance.

Is this zodiac compatibility test free?

Yes — the compatibility test is free to run and gives you a real synastry comparison between two birth charts, with dimension scores for love, communication, and long-term potential. Deeper AI-written relationship readings are available on top, but the core test costs nothing and needs no sign-up to try.

Can I test compatibility with just our birthdays?

Yes. Birth dates alone give a solid reading: every planet's sign except sometimes the Moon's is valid without a birth time, so Venus, Mars, and Mercury connections all compute. Adding birth times unlocks house overlays and Rising-sign dynamics — worth it if you have them, not a blocker if you don't.

Is this a free synastry chart?

Yes. Enter two sets of birth details and you get a free synastry chart comparison — planet-to-planet aspects between both charts, house overlays where birth times are known, and a compatibility score with a written reading. No sign-up and no payment for the core synastry report.

What does the birth chart compatibility score actually measure?

It weighs Sun signs for core temperament, Moon-to-Moon contacts for emotional rhythm, Venus and Mars for attraction and desire style, Mercury for communication, and Saturn contacts for staying power — then factors in whether the aspects between those planets are harmonious or challenging, plus house overlays when both birth times are available.

What is an astrology compatibility chart?

An astrology compatibility chart compares two birth charts using synastry — Moon, Venus, Mars, Rising signs, houses, and the aspects between them — to show how two people connect emotionally, mentally, and romantically.

How accurate is an astrological compatibility test?

A test that compares two full birth charts is far more accurate than Sun-sign matching, because it weighs Moon, Venus, Mars, Rising and house overlays instead of one placement. Exact birth times make it more precise.

What is moon sign compatibility?

Moon sign compatibility compares each person's Moon — emotional needs, comfort, and how they recover from stress. Strong moon sign matches usually mean easier day-to-day harmony, even when the Sun signs look mismatched.

Can I compare two birth charts for free?

Yes. Enter both birth dates, and times and places if you have them, and the compatibility calculator compares two complete charts instantly at no cost and with no sign-up.