Synastry Chart Calculator

A worked example: Maya and Daniel

Maya and Daniel are two made-up people. She was born on March 12, 1994 at 2:20 pm in Austin. He was born on November 3, 1992 at 7:45 am in Denver. Their Suns are in Pisces and Scorpio, two water signs that trine by sign, so their sign score is 91, near the top of the scale. Their full chart score is 70, in the Good band.

Most of their Moon contacts are easy, led by Maya's Mercury conjunct Daniel's Moon at half a degree, so the Emotional bar reaches 99. Conversation sits at 47. Maya's Saturn and Mars both square Daniel's Mercury at about half a degree, and her Mercury squares his Ascendant.

Their 12 tightest scored contacts

• Maya's Mercury square Daniel's Ascendant0.3°

  You misread each other's manner, and early talks may need a second try.

• Maya's Uranus sextile Daniel's Ascendant0.3°

  The Uranus person helps the Ascendant person feel freer about how they come across.

• Maya's Jupiter sextile Daniel's Uranus0.3°

  The Uranus person brings unexpected possibilities, and the Jupiter person is willing to give them a chance.

• Maya's Sun trine Daniel's Pluto0.4°

  The Sun person may find it easier to examine motives they'd usually defend when the Pluto person asks difficult questions.

• Maya's Venus opposition Daniel's Jupiter0.4°

  One of you may spend or promise past what's comfortable, and the other is happy to go along with it.

• Maya's Saturn square Daniel's Mercury0.4°

  Saturn can make Mercury feel foolish or unheard, and some subjects stop coming up.

• Maya's Mercury conjunction Daniel's Moon0.5°

  Mercury's owner can name what the Moon's owner feels, sometimes before they know it.

• Maya's Mars square Daniel's Mercury0.5°

  Words turn sharp here. Mars hears a challenge, and Mercury hears an attack.

• Maya's Venus trine Daniel's Mercury0.5°

  Compliments and small talk go well, so even disagreements stay polite.

• Maya's Neptune opposition Daniel's Mars0.9°

  The Mars person's directness meets the Neptune person's evasion, and frustration builds with no clear fight to have.

• Maya's Midheaven trine Daniel's Venus0.9°

  The Venus person may help through encouragement or social ease, and work events go better together.

• Maya's Uranus opposition Daniel's Mars1.6°

  Impatience runs high, and the Mars person can lose their temper at sudden changes of plan.

Their result lists 46 contacts, each with an orb and a short meaning. 6 of those are between two slow planets and stay out of the score.

How to read your result

1. Start with the score and its band: 90 and up is Excellent, 75 to 89 Strong, 60 to 74 Good, 40 to 59 Mixed, and under 40 Challenging.
2. Check the area bars next. Maya and Daniel score 99 for Emotional and 47 for Conversation, on a total of 70.
3. Read the tightest contacts first. A smaller orb means the angle is closer to exact, so it counts for more.
4. Check whose planet is whose. Your Venus trine their Mars isn't the same contact as your Mars trine their Venus. With every detail known, swapping the two people doesn't change the score.

For the longer version, including the houses their planets land in, see the guide to reading a synastry chart.

Why your sign score and full chart score differ

The two scores barely move together. Across 200 made-up pairs, the correlation between each full chart score and the sign score for the same two Suns was 0.08. The average gap was 20 points, and 154 of the 200 pairs fell in different bands.

The sign score compares your two Sun signs. The chart adds the Moon, the personal planets and, with a birth time, the angles. The zodiac compatibility calculator gives the quick sign answer.

The sample is 200 made-up pairs born from 1960 to 2005, at random times in 12 cities, using this calculator's provider and scoring code on November 3, 2026. Recomputing every contact ourselves, with the planets from NASA JPL's DE440s, gave the same score for 197 pairs and came within 1 point for the other 3. Counts describe these test pairs, not real couples.

What changes without a birth time

The Ascendant and Midheaven drop out, and the Moon gets less exact. Everything else stays close, because the other planets move slowly during a day. The Moon covers about 13 degrees a day, and on 43.9% of days from 1950 to 2025 it changed sign at some hour. So when a time is missing and the Moon could have changed sign that day, the result says so and lists the signs it could be in. The score still counts Moon contacts, read from the noon position, and those rows carry the words "at noon".

With both birth times removed from 100 of our test pairs, the score moved by 6 points in the typical pair, by 10 or more in 32 pairs, and by as much as 33 in one. It changed band in 45 of the 100. A birth certificate is the first place to look for a time.

A birth place matters less, unless you know the time. Without a place we calculate at Greenwich, and the second person takes the first person's place.

How the full chart score works

The result compares the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. With both birth times and places, it also compares the Ascendant and Midheaven. It lists conjunctions, sextiles, squares, trines and oppositions, and it doesn't show houses. The score adds those contacts up, leaving out any between two of Saturn, Uranus, Neptune and Pluto. Each one counts by the two bodies involved, the kind of aspect and how tight its orb is. Sun to Moon weighs the most, then Venus to Mars, then Moon to Moon. Trines and most conjunctions add, and sextiles add about half as much. Squares subtract, and oppositions subtract about half as much as squares, because an opposition also pulls two people together.

50 means the easy and hard contacts balance. Scores run from 35 to 99, and across our 200 test pairs the median was 68. The score measures ease rather than staying power: a conjunction with Saturn or Pluto subtracts, even though many astrologers credit Saturn contacts when a bond lasts.

How tight a contact has to be

An orb is how far an angle sits from exact. These are the widest orbs the calculation allows. A contact between a planet and an angle falls in between, from 5° to 8° for a trine.

Our calculation service runs on Lx Ephemeris, built on NASA JPL's DE440. Positions are tropical and geocentric. The score itself is our own calculation.

Two scores, and what each one reads

The full chart score, the wheel and the contacts are free here. A free account saves the pair and adds written readings, with room for five saved people. Compare your charts in the free app, where Pro adds Deep Compatibility with timing and love languages. The two-person PDF report is a separate one-time purchase. Sign-level answers for any pair are on pages such as Scorpio and Pisces compatibility.

Synastry calculator questions