Dashamsha, also written Dasamsa, is the tenfold divisional chart or D10. Each 30° sidereal sign is divided into ten 3° parts. This guide states the forward Parāśari sign rule used by our calculator and shows how to check its result by hand.
The odd and even sign rule
For Aries, Gemini, Leo, Libra, Sagittarius, and Aquarius, the first tenth maps to the natal sign. Count successive parts through the next nine signs in zodiac order. For Taurus, Cancer, Virgo, Scorpio, Capricorn, and Pisces, begin instead with the ninth sign counted inclusively from the natal sign, then move forward in zodiac order. The source is Bṛhat Parāśara Horā Śāstra, chapter 6, verse 13.
| D1 rāśi | Part 1: 0°–<3° | Part 4: 9°–<12° | Part 7: 18°–<21° |
|---|---|---|---|
| Gemini (odd) | Gemini | Virgo | Sagittarius |
| Scorpio (even) | Cancer | Libra | Capricorn |
The Gemini and Scorpio examples match P. V. R. Narasimha Rao's Vedic Astrology: An Integrated Approach, section 6.2.10. The book places 10° Gemini in Virgo and 19° Scorpio in Capricorn.
Boundary and degree examples
At 2°59′59″ Aries, the D10 sign is Aries. At exactly 3° Aries it becomes Taurus; at exactly 6° Aries it becomes Gemini. At 1°30′ Aries the derived D10 coordinate is 15° Aries. At exactly 30° Aries, the D1 sign becomes Taurus, an even sign, and the first D10 part begins in Capricorn, its ninth sign.
Let s be the zero-based D1 sign index and p the 0–9 index of its 3° part. The starting index is s for an odd sign or (s + 8) modulo 12 for an even sign. The D10 sign is (start + p) modulo 12; its displayed degree is ten times the offset inside the 3° part. This is a coordinate transform, not another observed sky longitude.
Why two D10 charts can differ
The Jagannatha Hora 7.63 release notes document additional D10 definitions, especially options reversing division order in even signs. Our calculator uses the conventional forward count from the ninth sign; it does not offer those alternate definitions. Check the stated D10 rule, ayanamsha, lunar-node convention, UTC instant, and ephemeris if another chart differs.
The D10 Lagna changes particularly quickly because it magnifies a narrow D1 ascendant interval. The tool flags positions within 0.1° of a 3° boundary. It requires a recorded birth time, latitude, longitude, and historical UTC offset. The astronomical base uses Astronomy Engine 2.1.19 and an approximate Lahiri conversion, not Swiss Ephemeris or a historical time-zone database. The local date input covers 1800–2100.
What D10 is used for
Jyotish texts and modern practice commonly relate D10 to work, public activity, and achievement. Rao's textbook names career and social achievement while reading D10 alongside the natal rāśi chart. This calculator gives placements so readers can compare the two; it does not predict promotion, income, or a career choice.
References
- Bṛhat Parāśara Horā Śāstra 6.13 — source verse and published translation of the odd/even start rule.
- P. V. R. Narasimha Rao, Vedic Astrology: An Integrated Approach — section 6.2.10 and worked examples.
- Jagannatha Hora 7.63 release notes — alternate D10 definitions in the author's software.
- Astronomy Engine 2.1.19 — library behind this site's D1 positions.