What is a good synastry score?

Higher than 56.7, which is the mean across 400 systematically sampled pairs of dates. That number is the whole point: scores of 70 and 80 sound impressive until you know that the average stranger pairing already scores in the fifties. We give you a percentile rather than a bare percentage.

Do I need birth times for synastry?

For a full reading, yes — aspects to the ascendant are a large part of classical synastry, and the ascendant moves a degree every four minutes. Without times we compute everything else and tell you what is missing rather than filling it in from midday.

How common is a Venus–Mars aspect between two charts?

Far more common than it is presented as being. Across our sampled pairs, the most frequent inter-chart aspects appear in 10 to 20% of random pairings — so one in five strangers has the aspect being sold to you as a soulmate signature. Every aspect in the result carries its own frequency.

Why do two synastry sites give different scores?

Because the weights are invented. There is no standard for how much a Moon trine outweighs a Saturn square, so every site makes its own scale. Ours is published on this page along with the orbs, and the percentile is more meaningful than the raw number precisely because it is relative.

Synastry Calculator: Chart Compatibility, Scored Against a Real Baseline

First chart

Date of birth Time (UTC, optional) Place

Second chart

Date of birth Time (UTC, optional) Place

Computed across 400 sampled pairs

The “rare” aspects are not rare

Synastry content leans hard on the idea that certain contacts are special. Here is how often the most frequent inter-chart aspects turn up between two arbitrary birth dates. One in five strangers carries the top one.

29% Jupiter trine Venus

18.3% Mercury square Saturn

18% Mars square Moon

17% Jupiter conjunction Venus

17% Saturn trine Venus

16.8% Mars trine Mercury

16.5% Mars trine Venus

16.5% Mars square Venus

Why some pairings recur: Mercury and Venus never stray far from the Sun, so aspects among those three are structurally more likely than chance would suggest. That is orbital mechanics, not affinity.

How the score is built — and why you should distrust every version of it

An aspect is an angle between two points, and only five are counted here: conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°), each with an orb of 5 to 8 degrees. That part is standard and mechanical.

The scoring is not. There is no authority establishing that a Moon trine is worth more than a Saturn square, so every site invents a scale, and none of them publish it. Ours multiplies three numbers: the aspect weight, the importance of each point, and how exact the angle is. It is a defensible scale and it is still arbitrary — which is exactly why the percentile matters more than the score. A relative position survives a change of scale; an absolute percentage does not.

What synastry cannot do

No inter-chart aspect has ever been shown to predict relationship outcomes. The frequencies on this page are the honest antidote: if the aspect being sold to you as a soulmate marker appears in a fifth of random pairs, it is not identifying your person, it is identifying a common angle between two slow-moving planets.

What the technique is genuinely good for is naming a friction you had not put words to. A chart that says “one of you needs reassurance faster than the other offers it” is a useful prompt whatever produced it. Use it that way, and check both birth times before you take the ascendant contacts seriously.

How this was produced

Longitudes for Sun, Moon and Mercury through Saturn, plus the ascendant where a time and place are given. Aspects are angular separations within the stated orbs. The baseline is 400 pairs on a deterministic date grid — steps of 137 and 211 days, chosen coprime to the year and the lunar month so the sampling does not resonate with either cycle.

The grid is reproducible: same steps, same start date, same numbers every time. No random sampling is used anywhere on this page.

The point weights are our own and unavoidably arbitrary — trust the percentile, not the score. The baseline excludes ascendants, so aspects involving one carry no frequency figure rather than an invented one.

Range: Baseline sampled from 1950 onward; planetary model valid 1800–2050 · Full method and stated accuracy

Sign compatibility The simpler sign-to-sign version, when you only have two star signs. Check your ascendant Before trusting ascendant contacts — see how much your birth time decides. One chart in full All placements and houses for a single birth date.

Synastry calculator

The “rare” aspects are not rare

How the score is built — and why you should distrust every version of it

What synastry cannot do