Astro Compatibility Calculator
Zodiac Sign Compatibility Calculator works out Canonical pair key and Separation between the signs from Comparison method, First sign and Second sign. The default figures on this page give classical aspect of Semi-sextile; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Canonical pair key: Aries and Taurus sorted by zodiac order give "aries|taurus".
- Aries is sign 0 and Taurus is sign 1, so they are 1 sign apart = 30 degrees.
- 30 degrees is the Semi-sextile: Disjunct - no Ptolemaic configuration.
- Fire and Earth are of opposite polarity; modality Cardinal vs Fixed.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
2 sources
What the Zodiac Sign Compatibility Calculator calculates
Canonicalises a pair of zodiac signs and returns the classical configuration between them - aspect, element, modality and polarity - plus the circular midpoint of two chart longitudes.
How to use this Zodiac Sign Compatibility Calculator
Enter Comparison method, First sign, Second sign and Context. Canonical pair key updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Canonical pair key, Separation between the signs and Classical aspect.
The method follows Claudius Ptolemy, Tetrabiblos, Book I (translated F. E. Robbins, Loeb Classical Library 435) and S. Carlson, "A double-blind test of astrology", Nature 318 (1985) 419-425.
Research case compat-pair-symmetric-a example
With First sign: Aries, Second sign: Taurus, Context: general, the calculator returns Canonical pair key: aries|taurus, Compatibility narrative status: EDITORIAL_RUBRIC_REQUIRED, Separation between the signs: 30. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Canonical pair key, Separation between the signs and Classical aspect. The inputs you can vary are Comparison method, First sign, Second sign, Context, First chart longitude and Second chart longitude.
Understanding Canonical pair key, Separation between the signs and Classical aspect
Sign compatibility is an entertainment convention with no demonstrated predictive validity. Nothing here should be used to make a decision about a relationship.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
What information do I need for the Zodiac Sign Compatibility Calculator?
You need Comparison method, First sign, Second sign, Context, First chart longitude and Second chart longitude. The page opens with default figures that give classical aspect of Semi-sextile, so you can see the scale before entering your own.
What does this Zodiac Sign Compatibility Calculator show?
It shows Canonical pair key, Separation between the signs, Classical aspect, Ptolemaic relationship, Element relationship, Modality relationship, Shared polarity and Signs apart, with the working and any warnings for your entries.
Can I check how the Zodiac Sign Compatibility Calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.