D16 Chart Calculator (Shodasamsa)

Sixteen parts and three starting points

Find the part first: divide a body's degree inside its sign by 1.875 and round down, then add one. Part 1 runs from 0° to 1°52′30″, part 2 to 3°45′, and so on to part 16, which ends at 30°. Then find the start. Aries, Cancer, Libra and Capricorn are movable and count from Aries; Taurus, Leo, Scorpio and Aquarius are fixed and count from Leo; Gemini, Virgo, Sagittarius and Pisces are dual and count from Sagittarius.

Count the part number of signs from that start, the start itself being the first. Sixteen steps go once round the zodiac and four signs further, so the last four parts of a sign repeat the first four. Sixteen times the arc already covered inside the part gives the D16 degree.

Conveyances, comforts and happiness

Parashara's list of what each varga governs gives the shodasamsa to vehicles, and translations add the comforts and happiness that go with them. In the birth chart the fourth house, Venus and the Moon carry the theme of ease and home comfort; the shodasamsa is where classical readers turned for those same indications at a much finer grain, which is also why it depends so heavily on an accurate time. In practice it is read with the fourth house of the birth chart, which holds conveyances as well as the home, and with Venus, the significator of comforts and luxuries.

The callout on this page follows that practice: it names the D16's fourth house, its occupants and where its lord stands. The usual reading also notes the D16 lagna and its lord and the placement of Venus. None of these predicts a purchase, an accident or a journey; they describe, as one layer of a whole-chart reading.

The 1961 shodasamsa

Take the 1961 rising degree, 11°23′ of a fixed sign, Scorpio: the count starts at Leo. 11°23′ divided by 1°52′30″ is just over six, so the lagna is in part 7, and seven signs from Leo, Leo counted first, is Aquarius. The D16 lagna is Aquarius at 2°17′.

Counting from Leo too, the Sun's 27°25′ Scorpio is part 15 and lands on Libra, Venus's 16°33′ Scorpio is part 9 and lands on Aries, and the Moon's 3°18′ Aquarius, Aquarius being fixed as well, is part 2 and lands on Virgo. Capricorn is movable, so Jupiter at 13°07′ counts from Aries and reaches Libra in part 7, while Saturn at 4°17′, in part 3, reaches Gemini. The nodes, each 27°41′ into a movable sign (Cancer and Capricorn), share a part number and a start, and both fall in Gemini.

From the Aquarius lagna the fourth house is Taurus, and nothing occupies it. Its lord, Venus, sits in Aries, the third house. The Sun, Mars and Jupiter share Libra, the ninth; Saturn and both nodes share Gemini, the fifth.

A chart that moves with the clock

The example shows how thin these parts are. Its rising degree had entered part 7 by under 0°09′ of arc: a birth a few moments earlier would put the D16 lagna in Capricorn and shift every house by one. Jupiter is just as close to its own line, at 29°56′ of its D16 sign, about twelve seconds of birth-chart arc short of the next part.

For that reason the D16 is only as good as the birth time behind it. A time recorded to the nearest quarter hour is not enough to fix its houses, and a reading built on the shodasamsa should say so. The planets' D16 signs are steadier, except for the Moon, which crosses a part every few hours.

What the page leaves out

Some texts attach a presiding deity to each of the sixteen parts, in one order for odd signs and the reverse for even. This page does not print or interpret those names; it gives the chart, the fourth house and its lord.

The modern outer planets are not drawn. The shodasamsa sharpens one corner of the natal chart — comforts and conveyances — and says nothing on its own about when; that is the work of the dasha periods. Read it last, after the birth chart and the navamsa are understood, and lightly when the birth time is in doubt.

How is the shodasamsa chart calculated?

Find the body's part (1 to 16) by dividing its degree in the sign by 1°52′30″. Then count that many signs, starting from Aries for a movable sign, Leo for a fixed sign or Sagittarius for a dual sign. Multiply what remains inside the part by sixteen for the degree.

Is the D16 the same as the kalamsa?

Yes. Shodasamsa means a sixteenth part and kalamsa is its other classical name; D16 is the shorthand. All three mean the same sixteen-fold chart, counted from Aries, Leo or Sagittarius by sign type.

What is the D16 chart used for?

Brihat Parasara Hora Sastra assigns it to vehicles and comforts. Readers look at its fourth house and that house's lord, the D16 lagna and Venus, and read them with the birth chart. It describes; it does not forecast buying a car or any other event.

Why does my D16 chart change so much with a small time change?

Each part is under two degrees wide, so the lagna moves into a new one many times an hour. The whole D16 house wheel turns with it. Unless the birth time is known closely, treat the D16 houses as uncertain.

Why do Rahu and Ketu sometimes share a D16 sign?

The nodes always sit at the same degree in opposite signs. Opposite signs are of the same type — movable with movable, fixed with fixed — so both count from the same start and, with the same part number, land in the same D16 sign.