The Saptamsa (D-7) divides each 30° zodiac sign into 7 parts, then assigns each part a zodiac sign under a stated rule. Each part spans 30° ÷ 7 (about 4°17′08.57″). It is derived from the same birth longitudes as the D-1 chart; it is not a second observation of the sky.
The sign-assignment rule
For odd signs start with the same sign; for even signs start with the seventh sign counted inclusively. The segment width is a repeating fraction. Keep the original degree precision instead of repeatedly rounding each boundary to 4°17′.
For a degree d within a sign, the segment number is floor(d × 7 ÷ 30) + 1, with d at least zero and less than 30. Here “floor” means discard the fractional part. Count the starting sign as one. Keep sign assignment separate from interpreting what a planet means.
Worked example
At 10° Aries, floor(10 × 7 ÷ 30) + 1 gives segment three. Count Aries, Taurus, Gemini to get Gemini in D-7. At 10° Taurus, start with Scorpio, seventh from Taurus; the third sign is Capricorn. At a boundary, use unrounded longitude because small rounding changes can move the result to the adjacent segment.
These are invented longitudes for teaching the calculation, not a client’s chart or a claimed life outcome. Self-check: 20° Taurus gives segment 5, because floor(20 × 7 ÷ 30) + 1 = 5. Taurus is even, so the start is the seventh sign counted inclusively, Scorpio; the fifth sign from Scorpio is Pisces. Boundary check: the first segment ends at 30° ÷ 7 = 4°17′08.57″, so a planet at 4°17′05″ is still in segment one, while a boundary rounded to 4°17′ would wrongly place it in segment two.
What it is used for
Saptamsa is discussed in traditional readings about children and family continuity. It does not measure fertility, establish the sex or number of children, or predict pregnancy outcomes. Those uses would turn a symbolic classification into an unsupported medical claim.
Birth-time sensitivity
The divisional ascendant can change when the underlying ascendant crosses a segment boundary, and a D-7 segment is about 4°17′ wide. The ascendant moves about one degree every four minutes on average, so that is very roughly seventeen minutes of birth time. The real rate varies with latitude and sign, so treat this as an order of magnitude, not a tolerance. If the birth time is approximate, calculate at both ends of the plausible range and note which placements change.
A reading exercise with boundaries
For a family-related reading, first ask whether the person wants that topic discussed at all. Keep a worksheet of the D-1 and D-7 positions, but do not label a chart “childless” or infer a medical condition. Real family choices depend on consent, circumstances and appropriate healthcare, not a difficult-looking placement.
When two tools disagree, compare birth time and time zone, zodiac/ayanamsha, degree precision and the division rule before comparing interpretations. Because the D-7 boundaries are repeating fractions, check whether a tool rounds them; a one-degree ayanamsha difference is about a quarter of a segment. More decimal places do not repair an uncertain birth record.
Sources and related guides
Calculation reference: Brihat Parashara Hora Shastra, chapter 6, the section describing the sixteen divisions. The cited text documents the traditional scheme; it does not validate personal predictions. Our examples above show the arithmetic without reproducing the text’s promised outcomes. For context read what divisional charts are and how to compare them.