How It Works
The calculator reads each birthdate to find the Sun sign using standard tropical zodiac dates; Aries, for example, runs from March 21 to April 19.
Every sign has an element (Fire, Earth, Air or Water) and a modality (cardinal, fixed or mutable). Each sign pair is scored on how well those qualities combine, with a bonus for sharing a sign or sitting opposite each other on the zodiac wheel.
Moon and Venus signs are optional. Add both partners' Moon signs to include emotional compatibility, and both Venus signs to include romantic style.
Your reading includes
- An overall compatibility score and tier.
- The element and modality pairing of your Sun signs.
- Whether you are an opposite sign pair.
- Separate Sun, Moon and Venus layer scores.
What Is the Formula?
Score for one sign pair
- E: element harmony for the two signs, from the chart below.
- Mo: modality match: cardinal + mutable 80, cardinal + fixed 75, fixed + mutable 70, mutable + mutable 65, cardinal + cardinal 55, fixed + fixed 50.
- B: a bonus of 10 for the same sign, or 8 for opposite signs.
- ÷ 0.8: rescales the result, because the element and modality weights add up to 0.8.
Combining Sun, Moon and Venus
Only the layers you fill in are counted. Skip Venus, for example, and the formula drops that term and divides by 1.8 instead.
Element Compatibility Chart
| Element pairing | Harmony | Example signs |
|---|---|---|
| Fire + Air | 90% | Aries and Gemini |
| Earth + Water | 88% | Taurus and Cancer |
| Earth + Earth | 85% | Virgo and Capricorn |
| Water + Water | 82% | Cancer and Scorpio |
| Fire + Fire | 80% | Leo and Sagittarius |
| Air + Air | 78% | Gemini and Aquarius |
| Earth + Air | 50% | Taurus and Libra |
| Fire + Water | 45% | Aries and Pisces |
| Air + Water | 42% | Libra and Pisces |
| Fire + Earth | 40% | Leo and Virgo |
Compatibility tiers
- 85% to 100%: Celestial Soulmates
- 70% to 84%: Strong Cosmic Bond
- 55% to 69%: Promising Alignment
- 40% to 54%: Growth Oriented Pairing
- Below 40%: Challenging Dynamics
Worked Example
Person A was born on 28 March 1995 and Person B on 14 August 1997.
- Sun signs: 28 March is Aries (Fire, cardinal) and 14 August is Leo (Fire, fixed).
- Element: Fire + Fire = 80. Modality: cardinal + fixed = 75. They are neither the same sign nor opposites, so there is no bonus.
- Sun score: (0.5 × 80 + 0.3 × 75) ÷ 0.8 = 62.5 ÷ 0.8 = 78.1, which rounds to 78%.
- Add Moon signs Cancer (Water, cardinal) and Pisces (Water, mutable): (0.5 × 82 + 0.3 × 80) ÷ 0.8 = 81.25, which rounds to 81%.
- Combined: (78 + 0.8 × 81) ÷ 1.8 = 142.8 ÷ 1.8 ≈ 79.3, which rounds to 79%.
At 79%, the pair sits in the Strong Cosmic Bond tier, with their shared Fire element doing most of the work.