How We Calculate Your Synastry Score
What counts, how much, and how we check it.
The short version
We work out where the planets were at each birth, find every angle between your planets and theirs, and add those angles up by area of life. A program does all of it, and no person or AI changes the numbers. The weights are our own design. They are not an ancient rule and other sites use different ones, so treat the score as a summary rather than a measurement.
Positions
We use the Western tropical zodiac and Placidus houses by default, with Whole Sign as an option on your result. Far north or south, where Placidus can't be worked out, we use Whole Sign. We cover births from 1900 to today. Time zones and daylight saving come from your birth place and date.
We checked this site’s results against a professional reference ephemeris on 2,000 random pairs of charts: 135,267 aspects, with no missing aspect, wrong aspect type or wrong house. The largest difference in an orb was 0.0063°. We left out cases within 0.02° of an orb limit or house line, where a few arcseconds can move a planet either way.
Aspects
| Aspect | Angle | Orb | We call it |
|---|---|---|---|
| Conjunction | 0° | 8° | Strong either way |
| Sextile | 60° | 5° | Easy |
| Square | 90° | 7° | Tense |
| Trine | 120° | 7° | Easy |
| Opposition | 180° | 8° | Tense |
We only use these five aspects, so minor ones such as the quincunx aren't listed.
The score
Each aspect counts toward an area only if its two planets belong there:
| Area | Planet pairs | Share of overall |
|---|---|---|
| Attraction | Venus-Mars, Sun-Venus, Sun-Mars, Moon-Mars, Venus and Mars to the rising sign, Venus and Mars to Pluto and Uranus, Venus-Neptune, Venus-Venus, Mars-Mars | 20% |
| Talking | Mercury to Mercury, Sun, Moon, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and the rising sign | 20% |
| Feeling | Sun-Moon, Moon-Moon, Moon-Venus, Venus-Venus, Moon to Saturn, Jupiter, Uranus, Neptune, Pluto and the rising sign | 30% |
| Staying | Saturn to Sun, Venus, Moon, Mercury, Mars and the rising sign; Jupiter to Sun, Venus and Moon; North Node to Sun, Moon and Venus; Sun-Sun; Midheaven to Sun and Moon | 30% |
Friends or family: Shared energy replaces Attraction, using Sun-Sun, Sun-Jupiter, Mars-Jupiter, Venus-Jupiter, Sun-Mars, Sun-Venus, Venus-Venus and Mars-Mars.
Three things set an aspect’s value. The planet pair has a weight from 2 to 10. The angle adds or subtracts: trines and sextiles add, squares and oppositions subtract, and conjunctions add less when Saturn or an outer planet is involved. In the Couple view’s attraction area, tense angles count as a small plus, because that is often what spark looks like. Tighter aspects count more: an exact aspect counts in full, and one at the orb limit counts a quarter.
We then scale each area to a score out of 100. Attraction runs from 40 to 95 in the Couple view, and the other areas from 26 to 98. In 2,000 random pairs with both birth times, the overall score had a middle value of 72, and nine in ten fell between 60 and 82. With dates only it was 68, and nine in ten fell between 58 and 77.
So read a score against those ranges, not against 100. With both birth times, about 72 is typical; above 82 happens for roughly one pair in twenty, and so does below 60. A lower score means fewer Easy links in the areas we weigh, not that a pair cannot work. The links behind the number say more than the number does.
Without a birth time
We use 12:00 UTC on that date. The Moon may be up to about 16° off, so Moon connections count at half weight. If the Sun or Moon changed signs that day, the top of your result shows both. Rising signs and houses are left out.
Under 18
If either person is under 18, you only get the friends and family version, which leaves out attraction between planets and any romantic wording.