Birth Chart Compatibility: What to Compare First
Birth chart compatibility (synastry) compares two people’s charts to see how their planets interact. Start with the Moon signs (emotional needs), then Venus and Mars (love and desire), the Sun signs (core identity), and finally the aspects between one person’s planets and the other’s. Sun-sign compatibility alone misses most of the picture.
Two people are never simply “compatible” or “incompatible”. Synastry shows where a relationship flows easily, where it creates friction, and what each person needs to feel loved. Friction is not a verdict; it often shows where a couple grows.
Start with both charts. Enter your birth date, time and city. Free, no account, no email.
Calculate a birth chart1. Compare Moon signs: emotional needs
The Moon shows what each person needs to feel safe. Moons in the same element (fire, earth, air or water) usually understand each other easily; very different Moons need more explicit communication about needs. See What is a Moon sign?
2. Compare Venus and Mars: love and desire
One person’s Venus in harmony with the other’s Mars is a classic sign of attraction. Also compare Venus to Venus: similar love languages make everyday affection easier. See Venus and Mars sign meanings.
3. Compare Sun signs and rising signs
Sun signs show core identity and life direction; rising signs show day-to-day style. Harmony here helps with shared goals and with simply enjoying each other’s company.
4. Look at cross-chart aspects
- Sun–Moon conjunctions, trines and sextiles are among the most supportive long-term links.
- Venus–Mars contacts describe chemistry and attraction.
- Saturn contacts add commitment and seriousness, and sometimes a sense of restriction.
- Squares and oppositions show friction and attraction at the same time; they need conscious work, not avoidance.
5. Check the 7th house
Planets from one chart falling into the other person’s 7th house often strengthen the sense of partnership. Your own Descendant sign also shows what you tend to look for in a partner.
What compatibility astrology cannot tell you
It cannot tell you whether a relationship will last or whether someone is “the one”. It is a language for understanding differences and needs. Respect, communication and shared values matter more than any aspect.
Frequently asked questions
What is synastry?
Synastry is the comparison of two birth charts to see how one person’s planets interact with the other’s, used to understand a relationship’s strengths and challenges.
Is Sun sign compatibility enough?
No. Moon, Venus, Mars and the aspects between both charts usually say far more about how a relationship feels day to day.
Do I need both birth times?
Planet signs and most aspects work with birth dates alone. Houses, rising signs and the 7th house need accurate birth times for both people.
Are hard aspects bad for a relationship?
Not necessarily. Squares and oppositions bring friction but also attraction and growth. Many long relationships have them.
Want your relationship read from both charts? Our Love & relationships reading includes synastry: enter your partner’s birth details at checkout and get a personal written reading.
Calculate my birth chartAstrology is offered for entertainment and self-reflection. It does not predict events and does not replace professional medical, legal, financial or psychological advice.