Birth chart compatibility (synastry) calculator
Put two birth charts side by side and see where two people meet: each person's Moon, Venus and Mars signs, how the two Moon signs sit to each other, where each person's planets land in the other's chart, and which planets look at each other.
Date and place of birth for both people. Add birth times if you know them: they give each person's rising sign and make the house overlay more exact.
What the calculator compares
Everything here is worked out in the sidereal zodiac of Vedic astrology. For each person you see the Moon sign, the Venus sign and the Mars sign, and the rising sign when a birth time is given. Classical astrology names the Moon the mind, so the Moon comes first: it is where two people's moods and daily rhythms meet. Venus is read for desire and affection, Mars for drive and strength.
Then the two Moon signs are compared: the same sign, or one to seven signs apart, where seven apart means opposite. You also see each sign's element (fire, earth, air or water), so you can tell whether the two Moons share a temperament or balance each other.
Synastry and composite charts
Both are modern Western techniques for comparing two people. A synastry chart keeps the two charts separate and lays one over the other, so you can see how each person's planets touch the other's. A composite chart blends the two into a single new chart, built from the midpoints between each pair of planets, and reads it as the chart of the relationship itself.
We do the synastry kind, and we do it with the tools of classical Vedic astrology: sidereal signs, houses counted from the rising sign, and the classical planetary aspects. That keeps each person's own chart intact.
Houses and aspects between two charts
The house overlay shows where each person's Sun, Moon, Venus and Mars fall in the other person's houses. Classical Vedic astrology counts the houses from the rising sign, so when we have a birth time, we count from it. Without one, we count from the Moon sign, a long-standing practice when the time is unknown.
The aspects follow the classical rule: every planet looks at the 7th sign from itself. Mars also looks at the 4th and the 8th, Jupiter at the 5th and the 9th, and Saturn at the 3rd and the 10th. When one person's planet looks at the other's, the two are read as being in contact.
Why there is no score
Most compatibility calculators end in a percentage. Ours does not, on purpose. Two charts describe where two people meet easily and where they pull against each other, and every real pairing has both. A number would hide the part that is actually useful: knowing where the ease is, and where the work is.
Read the result as a map of your meeting points, not a grade. Nothing on this page predicts how a relationship will go. That rests with the two people in it.
Questions people ask
What is a synastry chart?
A synastry chart compares two birth charts by laying one over the other. It shows where one person's planets fall in the other's houses, and which planets in the two charts look at each other. Synastry is a modern Western technique; we work it out with Vedic signs, houses and aspects.
What is the difference between synastry and a composite chart?
Synastry keeps the two charts separate and compares them point by point. A composite chart merges them into one chart, made from the midpoints between each pair of planets, and reads that as the relationship. Both are modern Western methods. This calculator does synastry, so each person's own chart stays whole.
Why is there no compatibility percentage?
Because a score flattens the useful part. Every pairing has places where two people meet easily and places where they pull against each other. The calculator shows both, so you can see where the ease is and where the work is. It describes tendencies, not an outcome.
Why are the signs different from a Western compatibility app?
Western apps use the tropical zodiac, tied to the seasons. Vedic astrology uses the sidereal zodiac, measured against the fixed stars. The two are offset by about 24 degrees, so a planet can sit one sign earlier here than in a Western app. The planets are in the same place; only the sign boundaries differ.
Do we need both birth times?
No. Without a time, we count that person's houses from their Moon sign, a long-standing practice, and leave out their rising sign. With a time, the houses are counted from the rising sign and the overlay is more exact. If only one of you knows your time, each chart is counted its own way.
What is Moon sign compatibility?
It compares the two Moon signs: how many signs apart they sit, and which elements they belong to. Classical astrology names the Moon the mind, and Indian matchmaking has long given the two Moons close attention. Here it is one layer of the comparison, shown alongside Venus, Mars, the houses and the aspects.
Two charts meet best when you know your own.
The free reading looks at your whole chart, finds which planet carries your question, and names a small weekly practice for it.