How a Chaturthamsha D4 Chart Is Calculated

The Parāśari fourfold rule

Chapter 6, verse 9 of the Bṛhat Parāśara Horā Śāstra describes the lords of the four turyāṁśas as those of the sign itself and its kendras. A kendra lies at the first, fourth, seventh, or tenth position from a chosen sign. The verse also names Sanaka, Sananda, Kumāra, and Sanātana as presiding figures. The program applies the sign assignment; it does not infer meaning from those figures.

Place the first quarter, from 0° inclusive to 7°30′ exclusive, in the D1 sign itself. Place the second, from 7°30′ to 15°, in the fourth sign counted inclusively. The third, from 15° to 22°30′, uses the seventh. The fourth, from 22°30′ to just before 30°, uses the tenth. At exactly 30° the D1 sign has changed, and its first D4 quarter begins. The same pattern applies to odd and even signs; D4 has no parity switch.

This is the same assignment as the published twelve-sign D4 table. Its columns are sign assignments, not house placements in an individual's D4 chart; houses depend on the transformed Lagna.

Calculate a D4 position

Normalize a sidereal longitude to the range 0° through just under 360°. Let s be the zero-based sign index, where Aries is zero. Let d be the longitude within that sign. The quarter index q is floor(d ÷ 7.5), from zero to three. The target sign index is (s + 3q) modulo 12. A degree within the new D4 sign may be displayed as 4 × (d − 7.5q). This stretches the source quarter to a full 30° coordinate.

Take the course's example: Jupiter at 13°21′ Taurus has d = 13.35°. It is in quarter two, whose zero-based index is one. Taurus is sign index one; one plus three is four, or Leo. Within that quarter, 13.35° − 7.5° = 5.85°. Multiply by four to obtain the derived D4 degree 23°24′ Leo. The source explicitly gives the D4 sign Leo; the derived degree here follows this calculator's display convention.

Use and limits of the D4 chart

The Parāśara Jyotiṣa Course quotes the traditional association of D4 with bhāgya, fortune, and discusses property. A modern reading may compare the D1 fourth house and its ruler with the D4 Lagna and fourth house. These are interpretive conventions. One D4 placement cannot establish home ownership, financial security, or an inheritance.

The D4 Lagna is sensitive to the birth time because a change of 7°30′ in the D1 ascendant crosses a D4 quarter. The calculator flags all displayed points within 0.1° of a boundary. It uses an approximate Lahiri ayanamsha and Astronomy Engine 2.1.19 to derive D1 positions, then applies the Parāśari D4 mapping locally in the browser. It uses mean lunar nodes, and other ayanamsha or ephemeris settings may give different placements near boundaries. Enter the historical UTC offset explicitly; the tool does not retrieve a time-zone database. Local date inputs cover 1800–2100, with possible omission of mean nodes when conversion to UTC falls just outside the supported range.