Compatibility reading assessed: the five scores for all fifteen pairs

A compatibility reading turns two birth charts into numbers, and numbers sound precise. So we tested ours. We ran every pair in our example circle, fifteen in all, through the Charthood engine and looked at what the five scores do: how far they spread, which pairs surprise, and how easily they move. Robin and Sam’s scores check out against their published worked example. The rest is mixed, and we’ll say where.

The short verdict

How does the tally work?

There’s no hidden model. Each theme starts at 50 (Friction starts at 20). Every contact that belongs to a theme then adds or takes away up to 14 points, scaled by a weight: 1.00 for an exact aspect, falling to under 0.15 at the edge of its orb. The result is rounded and held between 4 and 98. The “How we score this” note on every comparison page says the same in plain words.

Which contacts belong where is a short, fixed list. Spark takes Venus–Mars, Mars–Mars, Sun–Mars, Mars–Pluto, Venus–Pluto and Venus–Uranus. Warmth takes Moon–Venus, Sun–Moon, Venus–Venus and similar, plus Jupiter to Venus or the Moon. Talk takes Mercury to Mercury, Moon, Sun, Jupiter or Venus. Staying power takes Saturn to Sun, Moon, Venus or Rising, plus the North Node to Sun, Moon or Venus. Friction takes tense aspects from Mars, Saturn, Pluto or Uranus to a personal point, and tense Mars–Mars, Sun–Sun or Moon–Moon. Across all fifteen pairs the engine finds 436 contacts, and only 177 of them feed any score. The rest are real, listed on the page, and unscored.

Two design choices matter. Spark and Friction can only go up from their start: nothing in the rules lowers them. A Spark of 54, the lowest we found, is not “below average”. It is as low as the scale goes in practice. And a conjunction counts as an easy contact for Warmth, Talk and Staying power, which is a judgement call.

The fifteen pairs, scored

Robin and Sam read Spark 61, Warmth 47, Talk 46, Staying power 58 and Friction 45, the same five numbers as in the worked example. That’s a useful consistency check: the engine isn’t drifting between pages.

Spread: how far apart the pairs sit

Talk has the widest range, 59 points. Spark has the narrowest, 28. No score reached the limits of 4 or 98, and none came close. Most sit between 40 and 70, which is what you’d expect from adding a handful of small adjustments to 50. A reading that always lands in the middle is honest about the evidence, but it’s also why you should read contacts, not numbers.

Which pairs surprise?

Robin and Sam are the example couple. Their ranks out of 15 (1 is the highest score) are Spark 14, Warmth 12, Talk 10, Staying power 9 and Friction 8. So the partners don’t top any theme, and they sit low on Spark. Meanwhile the highest Spark, 82, belongs to Sam and Ade, and the highest Talk, 83, to Robin and Maya. The lowest Talk, 24, is Sam and Maya, and the lowest Staying power, 32, is Maya and Lena, Robin’s sister and Robin’s mum in the example.

None of that is a shock if you remember what the numbers count. Spark rewards Mars, Venus and Pluto contacts, and friends or relatives can have them as easily as lovers. We looked at the Venus–Mars part of that in our study of Venus and Mars aspects. A compatibility reading doesn’t know who is married to whom.

Fragility: what a wrong birth time does

Birth times are often rounded or remembered wrongly. We moved all six times 30 minutes later and recomputed all 75 scores, then repeated it with no birth times at all, which is what you get if you don’t know them.

Of the 12 moves of 5 or more in the 30-minute test, 12 were in Staying power or Friction, the two themes that use the Rising sign. On average the Rising sign moves about a degree every four minutes, so a small time error shifts its contacts quickly. With no times at all, the Rising contacts disappear and every planet is placed at local noon, so the fast-moving Moon can land elsewhere too. That is why 19 of the 35 larger moves fall in those two themes and the rest in the others. Check any tool for this: ask what it does when the time is missing, and whether it tells you.

Clock time depends on that database. A wrong time zone or daylight saving rule shifts a birth time by an hour, which is the middle row of the table above.

What a compatibility reading doesn’t measure

It doesn’t measure how two people behave, what they want, or how they treat each other. It counts angles between positions in the sky. Descriptions of a contact are written in general terms, and psychologists call our readiness to accept general descriptions as personal the Barnum effect. Treat a good “fit” with the same suspicion as a bad one.

How should you use a compatibility reading?

1. Start with the list of contacts. The tightest few are the reading. Our guide to reading a synastry chart shows how.
2. Use the scores to find topics. A low Talk is a prompt to ask how you each like to be spoken to, not a ruling.
3. Check the inputs. Date, place, time zone, and whether each birth time is real or a guess.
4. Run it for people you already know well. If it describes nobody you recognise, stop trusting it.

Common mistakes

• Ranking people by one number. There is no overall score here, on purpose. Averaging five different things hides what each one says.
• Reading low Friction as better. It starts at 20, so it can’t show “none”.
• Skipping the birth time. It changes the tally, as the fragility table shows.
• Using it to decide whether to stay together. Your actual relationship is better evidence.

Try it, then decide

Get your own two charts from our free birth chart calculator, then run them through the compatibility tool. A free account compares you with anyone you save. The Circle plan compares any two people you have saved with each other, not only you with them. Positions come from astronomy-engine.