D12 Chart Calculator - Dwadasamsa Chart
A free dwadasamsa (D12) chart calculator — twelve parts of 2 degrees 30 minutes in every sign, counted on from the occupied sign itself.
The dwadasamsa is the D12, the chart of twelfth parts. Thirty degrees of a sign make twelve slices of 2 degrees 30 minutes. By default this calculator counts the parts from the sign itself and moves forward through the zodiac: a body in slice one keeps its rasi sign, one in the second goes to the next sign, and one in the twelfth reaches the sign just behind its own. The rule is identical for odd and even, movable, fixed and dual signs, so there is no seed sign to look up.
Twelve slices against twelve signs means the dwadasamsas of any one sign visit each sign of the zodiac exactly once. Brihat Parashara Hora Shastra gives this count from the same sign, two and a half degrees to a slice, and adds four presiding deities — Ganesha, the Ashvini Kumaras, Yama and Sarpa — that recur three times across a sign's twelve parts. The calculator draws signs, not deities; the names are given here as the text lists them.
Classically the D12 is consulted for parents: BPHS sets parents against the dwadasamsa in its list of the matters assigned to its sixteen divisions, and P.V.R. Narasimha Rao's textbook widens that to the blood relatives of the parents — uncles, aunts and grandparents. The D12 belongs to all four Vimsopaka groupings of BPHS, from the six-chart Shadvarga, where it is weighted 2 points out of 20, to the sixteen-chart Shodasavarga, where its share is half a point.
Eight D12 placements worked by hand
All eight bodies are taken from a sample chart cast for Chennai at noon IST on 1 January 1990, fabricated for illustration, not a real birth. For each body, row one is its rasi position and row two the slice it falls in and the sign that slice counts to.
| # | Body and step | Result |
|---|---|---|
| 1 | Ascendant, rasi position | Pisces 16 deg 28' |
| 2 | Ascendant, slice of 12 | part 7: Virgo |
| 3 | Sun, rasi position | Sagittarius 16 deg 51' |
| 4 | Sun, slice of 12 | part 7: Gemini |
| 5 | Moon, rasi position | Aquarius 6 deg 27' |
| 6 | Moon, slice of 12 | part 3: Aries |
| 7 | Mars, rasi position | Scorpio 16 deg 07' |
| 8 | Mars, slice of 12 | part 7: Taurus |
| 9 | Mercury, rasi position | Capricorn 2 deg 00' |
| 10 | Mercury, slice of 12 | part 1: Capricorn |
| 11 | Jupiter, rasi position | Gemini 11 deg 27' |
| 12 | Jupiter, slice of 12 | part 5: Libra |
| 13 | Venus, rasi position | Capricorn 12 deg 31' |
| 14 | Venus, slice of 12 | part 6: Gemini |
| 15 | Saturn, rasi position | Sagittarius 21 deg 55' |
| 16 | Saturn, slice of 12 | part 9: Leo |
To get the slice, divide the degree inside the sign by 2 deg 30', drop the fraction and add one; then count that many signs on, the occupied sign counting as one. Venus, 12 deg 31' into Capricorn, sits barely past the 12 deg 30' boundary, so it opens its sixth slice and reaches Gemini; under two arc-minutes lower it would have been in the fifth slice, which counts to Taurus.
How to read the result
In the divisional charts view, pick D-12_dwadasamsa from the selector above a chart cell. The selector is sorted by D-number, which places the key after D-11_rudramsa and before D-16_shodasamsa. The D12 is not among the charts shown by default, so switch one cell to it; the North Indian or South Indian setting applies to it as to the other cells.
Hover a body for its D12 sign and a degree. That degree is twelve times the body's degree inside its rasi sign, reduced below 30, so it starts near 0 when a slice has just begun and climbs towards 30 as the slice ends. In the sample, Venus reads Gemini : 0:21:27, having entered its slice a fraction of a degree earlier, while the Sun reads Gemini : 22:23:18. Mercury, Jupiter and Venus carry brackets in that sample because they were retrograde at the birth moment.
In reading the chart, the textbook by Narasimha Rao uses the 9th house of the D12 — its lord or its arudha pada — for the father and the 4th house for the mother, and then treats the rasi holding that lord as a lagna of its own. Amber tags in a D12 cell are this chart's own arudha padas, derived from the D12 placements, so the A9 and A4 drawn there are the padas that method reads.
Key terms
- D-12_dwadasamsa
- The D12's key in each cell's selector, spelt exactly as the chart menu shows it; choosing it draws the count-from-the-sign chart set out above.
- Dwadasamsa slice
- One twelfth of a sign, 2 deg 30' of arc; the slice number, 1 to 12, tells how many signs on from the occupied one the body is placed.
- D12 lagna
- The dwadasamsa sign of the ascendant degree, marked As in the cell; houses in this chart are counted from it.
- 9th and 4th of the D12
- Narasimha Rao's houses for father and mother in this chart, judged through their lords or through their arudha padas.
- Shadvarga
- BPHS's six-chart group — rasi, hora, drekkana, navamsa, dwadasamsa and trimsamsa — in which the D12 carries 2 Vimsopaka points out of 20.
- Parivritti
- A cyclic way of dividing a sign, in which the parts run on round the zodiac from one sign into the next; by default this calculator does not divide the D12 that way.
One count for every sign
No odd/even or movable/fixed switch: each sign starts its run at itself, so a single list of twelve steps covers the zodiac.
A boundary every 2 deg 30'
Twelve equal slices per sign make a D12 placement easy to confirm by hand, as the eight worked bodies above show.
Related to the D60 count
Like the D60 shashtiamsa, the D12 counts from the sign a body occupies; the D60 steps in half degrees, the D12 in two and a half.
Common questions
What is a dwadasamsa chart?
It is the D12: every sign divided into twelve parts of 2 deg 30', with each body moved to the sign its slice indicates, counting on from its own rasi sign.
Does the D12 count differently for odd and even signs?
Not by default. The run starts at the occupied sign and goes forward for all twelve signs. The engine also holds a variant that counts even signs backward, and parivritti schemes, but by default the D12 on screen uses the forward count.
Do I need my exact birth time?
For the D12 ascendant, yes. Each part spans 2 deg 30', and the ascending degree moves through an arc that size fast, so a birth time slightly off near a boundary can put the D12 lagna in the next sign. The Sun needs two to three days to cross one part, so planetary D12 signs are far steadier.
How do I find a D12 sign by hand?
Divide the degree within the sign by 2.5, drop the fraction and add one to get the part number. Step that number of signs forward, the occupied sign being step one. Narasimha Rao's textbook works a Mercury placed at 11 degrees Gemini this way: fifth part, Libra; the calculator agrees.
Which deities rule the twelve dwadasamsa parts?
BPHS names four, Ganesha, the Ashvini Kumaras, Yama and Sarpa, in that order, repeated three times across a sign. The calculator does not display them; they are listed here just as the text gives them.