What Is a Synastry Chart? Birth Chart Compatibility

After you discover your birth chart, exploring a synastry chart (or zodiac compatibility) is naturally the next frontier. How do astrologers deem one couple astrologically compatible? To examine love compatibility, many astrologers use the technique of synastry charts to compare two (or more) birth charts with one another. (If you’re not certain of your own birth chart, we offer a free birth chart calculator to help you out.)

Sounds simple enough, right? Well, once you add in the zodiac signs, elements, planets, houses, and aspects, it’s easy to see how complex the ancient art is. Let’s break down some synastry basics so you’ll be able to take a deeper dive into the world of natal chart compatibility.

What Is a Synastry Chart?

During a synastry chart reading, astrologers layer two or more charts on top of one another. The two charts create a bi-wheel, with the inner ring as the helm of the chart and the outer chart showing where those planets land in the first person’s birth chart. 

Let’s imagine you are a Cancer rising with a Cancer moon (hello, sentimentality and feelings!), and your partner or crush has a Cancer sun. With your chart in the center and your potential beau’s layered around your chart, you’d notice that their sun in Cancer lands in your first house and sits near your moon in Cancer. This is synastry gold!

Here are a few considerations astrologers rely on for analyzing the synastry and love compatibility between people.

Astrology Compatibility in a Synastry Chart

House Placement. Figuring out planet and house placement across a synastry chart helps determine how each partner makes the other feel. It also indicates the “vibe” of the relationship. Let’s say your partner’s sun and Mercury are in your ninth house. This is a relationship that will demand expansion (teaching, learning, traveling)—you’re meant to grow and learn together.

Zodiac Signs and Elements. There is something to be said about having planets and placements in like-minded elements. For example, if you’re someone with a lot of water sign and earth sign placements, you may naturally be more in touch with your emotions and approach new situations with caution. That might be difficult to understand for someone who’s birth chart is full of fire and air sign placements—who seeks a new, spontaneous adventure every day.

Aspects. The aspects of a birth chart or synastry chart detail the type of interaction two planets will have. If your moon is conjunct someone else’s sun, there is an instant connection and understanding of one’s sense of self and inner world. But if your moon is square someone else’s sun, there is a differing of inner and outer expressions. There is nothing wrong with having tense aspects together; they may just indicate challenges.

Planets. This part of synastry really matters. If someone has Saturn (restriction and hardship) sitting on top of your moon (emotions), it may be more difficult to feel like your emotional world is supported. But if someone has Jupiter (expansion) in the same sign as your moon, it will be easier to feel emotionally supported. Astrologers look to various planet combinations to understand challenges and strengths in partnership.

Zodiac Sign Compatibility in a Synastry Chart

As you look at the four major points above, you’ll want to take into consideration the zodiac sign connections as well. When exploring synastry or love compatibility, zodiac sign compatibility is an excellent place to start. Understanding how the various elements interact with one another will offer a solid foundation in love compatibility basics. (Remember, it’s much more complex, but this is a great place for our astro-curious folks to begin.) 

When approaching this topic, it isn’t like: fire signs must do well with fire signs. Think about it: Sometimes opposites really do attract, and it’s important for our partners to bring a differing perspective to inspire self-reflection and growth within us. 

As a general rule of thumb, many astrologers will say that fire signs (Aries, Leo, and Sagittarius) and air signs (Gemini, Libra, and Aquarius) match well together. Fire feeds air and their energy works well together. Earth signs (Taurus, Virgo, and Capricorn) and water signs (Cancer, Scorpio, and Pisces) also have a natural ease with one another. If you think about your houseplants, they require water to thrive and grow. We see the same thing here in the astro-realm.

Synastry Chart Compatibility Test

Everyone wants to know, “Are we meant to be?” and the truth is, every relationship we enter teaches us a lesson. Curious whether you and your partner share similar emotional values? Here are some key aspects to look for in birth chart compatibility. 

• Moon-Venus Aspects. The moon is what we need to feel comfortable and secure. When someone’s Venus (love and values) meets the moon, there is a shared sense of security. This is quite a romantic aspect that’s hard to beat.
  
• Sun-Venus Aspects. When someone’s sun (identity) meshes well with another person’s Venus, there is a strong potential for love and commitment. One’s value system is reflected in the other’s personality and sense of self.
  
• Sun-Moon Aspects. When the two luminaries connect, there is a soft and supportive aspect. This provides an instant mutual understanding. The sun person’s outer expression syncs with the moon person’s inner world and emotional core. Both intuitively know what the other needs.
  
• Mercury-Mercury Aspects. Communication is key in any partnership! If you aren’t able to talk through your problems, that’s more than a red flag. Mercury is also involved in our daily tasks and lives—how we like to organize and how we approach various situations. Having a sweet Mercury connection with a partner ensures for a smoother ride when life throws difficulties your way.
  
• Saturn Aspects. Saturn is the planet of karma and the lord of time. While Saturn can be quite the Debbie downer, it brings hardship so you can make it through difficult times together. Not all Saturn aspects are created equal. But with a softer aspect (like a trine or sextile) to another’s personal planet, this can be a strong indicator for commitment. 

More on Synastry Charts

While synastry is quite complex, there’s always more to explore. It’s also important to note that synastry readings aren’t solely limited to love relationships. You can calculate your synastry with your family members, friends, co-workers, and more. So, go pull up some charts and find which aspects resonate most for you!