Porondam Matching Sri Lanka — Horoscope Compatibility

In Sinhala Buddhist and Tamil Hindu tradition, before a proposal proceeds both horoscopes (kendara) are checked for porondam — the eight kootas of the classical Ashtakoota (Guna Milan) system, totalling 36 gunas. This tool computes them from first principles instead of a printed litha, so the working is transparent and reproducible.

1. Find each Moon position.Each birth date and time is treated as Sri Lanka local time (UTC+5:30, no daylight saving), converted to a Julian Day, then to the Moon's apparent geocentric longitude via the periodic series of Jean Meeus, Astronomical Algorithms (Chapter 47). The Lahiri ayanamsa is subtracted for the sidereal longitude: λ_sidereal = λ_tropical − ayanamsa.
2. Read the star and sign. The nakshatra index is floor(λ_sidereal / 13.3333) (27 stars of 13°20′) and the rasi is floor(λ_sidereal / 30) (12 signs of 30°). Each rasi has a fixed lord — Aries→Mars, Taurus→Venus, … Pisces→Jupiter.
3. Derive the fixed attributes.Each nakshatra maps to a Yoni (one of 14 animals), a Gana (Deva / Manushya / Rakshasa) and a Nadi (Aadi / Madhya / Antya). Each rasi maps to a Varna (Brahmin > Kshatriya > Vaishya > Shudra) and a Vashya group. These come from the standard Jyotisha tables.
4. Score the eight porondam(groom = boy, bride = girl), with rising weights:
   • Varna (1): 1 if the boy's varna rank is not below the girl's, else 0.
   • Vashya (2): from the 5×5 vashya-group matrix.
   • Tara/Dina (3): count the stars between the two nakshatras each way; each direction that avoids the Vipat (3), Pratyari (5) and Vadha (7) taras scores 1.5.
   • Yoni (4): 4 for the same animal, 0 for a sworn-enemy pair, else neutral 2.
   • Graha Maitri (5): friendship of the two rasi lords → 5, 4, 3, 1, 0.5 or 0.
   • Gana (6): from the gana matrix (same 6, Deva–Manushya 5, Deva–Rakshasa 1, Manushya–Rakshasa 0).
   • Bhakoot/Rasi (7): 0 if the rasis form a 6/8, 5/9 or 2/12 pair (dosha), else 7.
   • Nadi (8): 8 if the two nadis differ, 0 if identical (Nadi dosha).
5. Total and verdict. The eight sum to a score out of 36: below 18 not recommended, 18–23.5 average, 24–31.5 very good, 32–36 excellent. Nadi and Bhakoot dosha are shown separately, because a high total can still carry a dosha.

Only the geocentric Moon longitude is used — the sub-1° parallax is immaterial next to the 13°20′ star width, so no birthplace is needed. On the Yoni porondam, the finer friendly/enemy sub-tiers vary between classical schools, so this tool scores only the two universally-agreed outcomes (same animal 4, sworn-enemy 0) and treats every other pairing as neutral. An internal cross-check confirms the eight koota points re-sum to the reported total and that the dosha flags agree with their scores.

• Drik Panchang — Ashtakoota Guna Milan (Kundli Matching) methodology
• List of Nakshatras — 27 stars with Yoni, Gana and Nadi attributions
• Ayanamsa — Lahiri / Chitra-paksha sidereal correction
• Jean Meeus — Astronomical Algorithms (Moon-position periodic series, Ch. 47)

The Moon-position pipeline is the one validated in the nakshatra tool (Meeus Example 47.a). The koota weights, dosha rules and score bands follow the standard Ashtakoota Guna Milan methodology and were last cross-checked on 2026-07-02. The porondam are a traditional check only — not a prediction, and not a substitute for a family astrologer's reading of the full horoscopes.