Kaal Sarp Dosha is a question of geometry. When your chart has it, here is how close the call was.

Underneath Kaal Sarp Dosha is a test simple enough to check with subtraction, which makes it something to measure rather than worry about.

What the rule checks

Rahu and Ketu are not bodies. They are the two points where the Moon's path crosses the Sun's, always exactly opposite each other - in this engine Ketu is Rahu plus 180 degrees by construction. Together they draw one line across the chart, cutting the zodiac in two.

Kaal Sarp is present when all seven classical grahas - the Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn - lie in the same half. Rahu and Ketu are not counted, because they are the line.

The arithmetic is one subtraction per graha: how far it sits forward of Rahu, from 0 to 360 degrees. All seven strictly between 0 and 180 puts them on the arc from Rahu to Ketu; all seven strictly between 180 and 360, on the arc from Ketu to Rahu. Anything else and the combination is absent. No houses are involved, so the verdict needs no birth place.

A worked chart, and a very close call

This app's own test chart is a birth at 12:00 IST on 12 January 1997, with Rahu at 158.6469 degrees.

Present - but look at the ends. Mars is 0.0938 degrees past Rahu, under six minutes of arc, and Saturn is 0.577 degrees short of Ketu. The verdict is correct and very nearly not true, and a bare yes hides that.

So when the combination is present, the calculator also reports the margin: the graha nearest either end of the axis, and by how many degrees - here, Mars, 0.09 degrees from Rahu. Sampling this engine at noon IST on every day from 1970 to 2014, the combination was present on 1,216 of 16,436 days, about 7.4%. Of those, 75 had a margin under 2 degrees, and 39 under 1.

A chart where the answer is plainly no

Most charts are nowhere near the line, and it helps to see one. The birth on 15 August 1990 at 10:30 IST in New Delhi, used throughout these essays, has Rahu at 282.76 degrees, in Capricorn. Measured forward from Rahu, Mars is 104.73 degrees on, the Moon 126.16, Jupiter 172.88 and Venus 175.10 - all on the Rahu-to-Ketu arc - while the Sun is at 195.64, Mercury at 222.69 and Saturn at 343.33, on the other. Three grahas on one side and four on the other: not present, and not close. With the place resolved, the calculator adds that Rahu is in the 5th house and Ketu in the 11th. The Rahu in the 5th house and Ketu in the 11th house pages describe what the classical texts read from those placements, which is a different and much older kind of reading.

Why it comes in runs of about two weeks

The 7.4 percent figure hides a pattern that explains a great deal about the combination. Six of the seven grahas move slowly relative to the axis, and one, the Moon, goes all the way round every 27 days or so. For the combination to be possible at all, the six slower ones - the Sun, Mercury, Venus, Mars, Jupiter and Saturn - must already sit together in one half. When they do, the Moon spends roughly half of each month in that same half, and for those days the combination is present; for the other half, it is not.

The daily scan from 1970 to 2014 shows exactly that. The 1,216 present days came in 102 separate runs, with a median length of 13 days and a longest of 15. And the runs cluster in seasons: only 23 of the 45 calendar years had any present day at all at noon IST, while the busiest years - 1986, 2004, 2013, 1977, 1978 and 1976 - had between 67 and 80 days each. In the other 22 years, the six slower grahas were never gathered in one half of the axis, and no birth that year could have the combination.

So whether a person "has Kaal Sarp" depends overwhelmingly on the year and the fortnight they were born in, which they share with everyone born in that window - about half the days of a season. It is a feature of the sky over a span of time, not of an individual birth moment. That is also why the verdict so rarely depends on the time of day: in the scan it differed between 00:00 and 23:59 on only 1.24 per cent of days, the days on which the Moon happened to cross the axis.

Which graha usually decides the margin

Among the 1,216 present days, the graha nearest either end of the axis - the one that sets the margin - was the Moon on 250 days, Saturn on 245, Jupiter on 222 and Mars on 217, but Venus on only 124, Mercury on 105 and the Sun on 50. The pattern makes sense: when the combination holds, the Sun and its two close companions tend to sit together well inside the half, while the outer planets and the Moon more often mark its edges. If your chart has the combination, the margin row tells you which of them it was, and a margin set by the Moon is the one most sensitive to birth time.

How close the typical call is

The same scan gives the full spread of margins on the present days. The median margin was 13.1 degrees: half of all positive charts had some graha within about 13 degrees of one end of the axis. A quarter were within 6.1 degrees, 230 of the 1,216 within 5 degrees, and 502 within 10. The widest margin found was 60.4 degrees. So the 1997 test chart, at 0.09 degrees, is an extreme, but a margin of a few degrees is ordinary - which is why the calculator reports it every time the answer is yes, rather than only when it is dramatic.

Which Rahu?

Rahu can be placed two ways. The mean node is a smoothed average; the true node adds the periodic swings either side of it. This app uses the mean node everywhere and the calculator keeps it, but it also computes the true node for your birth moment and runs the test again.

The two are at most about 1.88 degrees apart across those years, which is enough on a close call. In the worked chart the true node sits 1.26 degrees back, putting Saturn 180.69 degrees past Rahu: over the line. Of the 1,216 positive days, 32 flipped like this, roughly one in forty. No text in this app's library says which node the rule intends, so the calculator keeps its verdict on the mean node, says what the true node would have given, and calls such a chart a genuine borderline case.

A graha exactly on the line

Positions are published to four decimal places, so occasionally a graha sits exactly on Rahu or Ketu. A minute-by-minute search of every crossing of the axis by the seven grahas between 1970 and 2015, re-run on 12 October 2026 on the current engine, found 73 such minutes, eight of them in charts that would otherwise be positive. (An earlier, narrower search on the previous version of the engine had counted 26 and four.) No source says whether on the line counts as inside. This app counts it as outside, the strict test it has always used, and says so when that choice decided the answer. At 05:54 IST on 17 July 1979, Saturn sits exactly on Rahu with the other six on the Ketu-to-Rahu arc: the calculator returns not present and tells you to treat the chart as borderline. That is a policy, not a finding.

Why it names no type, and says nothing about Kaal Amrit

Popular practice divides Kaal Sarp into twelve named types - Anant, Kulik, Vasuki and the rest - and calls one of the two directions Kaal Amrit. This calculator does neither, and says why in its own output.

The reason is a search result. None of the searchable astrology texts in this app's library - BPHS, Saravali, the Bhrigu Sutras, Daivajna Vallabha and Advanced Predictive Astrology - contains any spelling of Kaal Sarp. The Sarpa Yoga that BPHS and Saravali describe is a different rule, malefics alone in the angular houses, computed separately in the yogas calculator. Two more books are image-only scans that could not be searched, so the claim covers what was searchable and no more. What the engines are actually built from is listed, with chapter and code location, on the sources page.

A type name would have had to come from general knowledge and then be printed in this app's voice as if it were sourced. The direction is reported as a plain fact for the same reason, and that matters: of the 1,216 positive days, 517 had the grahas on the Rahu-to-Ketu arc and 699 on the Ketu-to-Rahu arc. Whichever side a naming scheme calls Kaal Amrit, it relabels hundreds of those charts, and nothing in the library says which side that is.

What the classical texts do say about Rahu and Ketu

The absence of the name does not mean the texts ignore the nodes. They treat them at length - just not as a line that encloses the other planets. It is worth seeing how, because it is a different way of reading the same two points.

• BPHS Chapter 3 describes Rahu with a smoky appearance and a windy temperament, and says simply that "Ketu is akin to Rahu" - two points, each with its own nature, alongside the seven grahas.
• BPHS treats both as always retrograde. Chapter 31 counts their Argala in reverse for that reason, and Chapter 47 says their dasha effects are realised in reverse order.
• BPHS Chapter 34, Slokas 16-17, gives the general rule for reading them: they "give predominantly the effects" of the house they occupy and of the house lord they are joined with, and a node in a kendra associated with the lord of a kendra or trikona becomes a yoga karaka - a planet that produces good results.
• BPHS Chapter 47 records two views on their own signs and gives their exaltation as Taurus for Rahu and Scorpio for Ketu, then describes each one's dasha conditionally on placement. Chapter 48 adds, in a brief aside, that Rahu and Ketu give favourable results in the 3rd, 6th and 11th houses.

So the classical reading of a node is individual and conditional: this node, in this house, with this lord. That is the reading the planet-in-house pages give - for Rahu, Rahu in Vedic astrology and its twelve house pages; for Ketu, Ketu in Vedic astrology; and for their periods, Rahu Mahadasha and Ketu Mahadasha. Kaal Sarp asks a different, purely geometric question about the whole chart, and the texts in this library do not ask it.

The axis by house, when a place resolves

With a birth place, the calculator adds which houses Rahu and Ketu occupy. Because they are always opposite, there are only six possible axes: 1st and 7th, 2nd and 8th, 3rd and 9th, 4th and 10th, 5th and 11th, 6th and 12th, with either node at either end. This is where the classical reading picks up, house by house, in the terms of BPHS Chapter 34: the node gives the effects of the house it sits in and of the lord it joins. In the 1990 chart the axis runs 5th to 11th, with Ketu in the 11th - one of the three houses, the 3rd, 6th and 11th, where the BPHS aside in Chapter 48 says the nodes give favourable results. That is a reading about the nodes; it is not a reading about Kaal Sarp, and the calculator does not merge the two. The 5th house and 11th house pages give the houses' own significations.

The direction is reported for the same reason the houses are: as a fact. Of the 1,216 present days in the scan, 517 had the grahas on the Rahu-to-Ketu arc and 699 on the Ketu-to-Rahu arc. Nothing in the library gives either direction a different meaning, so the calculator gives neither one a different label.

The axis moves backwards, about 19 degrees a year

The engine computes Rahu as the mean node, which slides backwards through the zodiac at a steady rate: between 1 January 2000 and 1 January 2001 it moved 19.40 degrees back. At that rate the axis goes all the way round in about 18.6 years and changes sign roughly every year and a half. Because the six slower grahas must gather in one half of a moving line, the seasons in which the combination can occur come and go with the combined motion of the node and the outer planets - which is why the scan found it possible in some years and impossible in others, with no simple calendar rhythm a reader could use.

Sarpa Yoga is a different rule

The similar name causes confusion, so it is worth stating the classical Sarpa Yoga exactly. BPHS Chapter 35, Sloka 8, lists it among the two "Dala" Nabhasa yogas: when three kendras are occupied by benefics, the yoga is Maala; when malefics are so placed, it is Sarpa, or Bhujanga. It is a rule about which planets occupy the angular houses, counted from the ascendant. It says nothing about the nodes as a boundary and nothing about all seven grahas being on one side. The engine computes it separately, in the yoga calculator, following that BPHS wording, and What a yoga in your chart means explains how it reads it.

Checking it by hand

Because the test is one subtraction per graha, it can be checked with any chart that prints longitudes - the birth chart calculator does.

1. 1.Write down the sidereal longitude of Rahu, from 0 to 360 degrees measured from the start of Aries. (A sign and degree converts by adding 30 for each sign after Aries: 12.76 degrees of Capricorn is 270 + 12.76 = 282.76.)
2. 2.For each of the seven grahas, subtract Rahu's longitude from the graha's. If the answer is negative, add 360. That is how far the graha sits forward of Rahu.
3. 3.If all seven answers are strictly between 0 and 180, the grahas are all on the Rahu-to-Ketu arc. If all seven are strictly between 180 and 360, they are all on the Ketu-to-Rahu arc. Either way the combination is present.
4. 4.If some are below 180 and some above, it is absent. Stop there.
5. 5.If it is present, the margin is the smallest of these distances: each answer itself, 180 minus each answer below 180, each answer minus 180 for those above, and 360 minus each answer. The graha that gives the smallest is the one nearest the line.

Done for the 1990 chart, step 3 fails at once: Mars at 104.73 and the Sun at 195.64 are on opposite sides. Done for the 1997 test chart, every answer is between 0 and 180, and the smallest distance is Mars's 0.0938 from Rahu. If your hand result and the calculator's differ, the usual reason is a different Rahu - mean or true - or a graha within a fraction of a degree of the line.

Reading your own result in four steps

1. 1.Read the verdict and the direction as facts about where the grahas sit, nothing more. Neither carries a prediction, and the calculator's own reading sentence says the same.
2. 2.If it is present, read the margin and the graha that sets it. A margin of many degrees is settled; a margin under a degree or two is close.
3. 3.If the Moon sets the margin, compare the margin with your birth-time uncertainty at about half a degree an hour.
4. 4.Check the true-node line. If it says the true node would flip the verdict, the chart is borderline on any method, and no amount of birth-time precision changes that.

Choices the engine makes, stated plainly

• Seven grahas, not nine. Rahu and Ketu define the line, so they cannot be on one side of it; the outer planets beyond Saturn are not part of this system at all.
• The mean node. It is used everywhere in the app, and the true node is computed only as a check. On the 1,216 positive days in the scan, 32 - about one in forty - would have flipped on the true node, and the calculator says so when yours is one of them.
• Strictly inside. A graha exactly on the axis counts as outside, and the calculator says when that choice decided the answer.
• All or nothing. The engine computes no "partial" form with one graha outside the arc. No text in the library defines one, so none is reported.
• No houses in the verdict. Houses are added to the description when a place resolves, but the yes or no never uses them.

Where else the verdict appears

The same function feeds the dosha list of the full kundali and the Mangal Dosha calculator, and the confidence and risk engine counts a present result as one weighted term among many, at the same weight it gives a Moderate Mangal Dosha. Nothing in the app turns it into a date, a forecast or a remedy. The kundali feature page describes the full chart view where the list appears.

What the result is not

• Not a prediction. It reports sides, degrees and a margin, nothing about what will happen in your life, and it attaches no remedy, because no outcome is being promised or averted.
• Not a strength score. A margin of 0.09 degrees is not a weaker Kaal Sarp; it is a closer call on whether the rule applies at all.
• Not a house reading. A resolved birth place adds which houses Rahu and Ketu occupy. Without one, no houses are shown rather than guessed, and the verdict never used them.

Before you run it

The calculator needs a birth date and a birth time. The Moon moves about 13 degrees a day, and across the same years the verdict differed between 00:00 and 23:59 IST on 204 of 16,436 days, 1.24%. The calculator reads only the time you give, so if yours is a window rather than a minute, run it at both ends. What an unknown birth time costs covers the rest of the chart. Without a birth place, the time is read as India Standard Time.

The time sensitivity has a simple shape. The only graha fast enough to cross the axis within a day is the Moon, at roughly half a degree an hour; the others move a degree a day or less. So a birth window matters only if the Moon is near Rahu or Ketu during it. If your result is present and the margin row names the Moon, divide the margin in degrees by about half a degree to get the number of hours your birth time could be wrong, in that direction, before the answer changes. If the margin is set by any other graha, a few hours of error will not change it.

One day on which the time decided it

Here is one of those days, found by scanning the engine for a present result whose margin was set by the Moon. On 16 January 1985 the six slower grahas were already gathered on the Ketu-to-Rahu arc, and the Moon was approaching Ketu from the other side. Stepping through the day in ten-minute steps, the verdict is not present until 09:40 IST, when the Moon crosses Ketu and joins the others; from then on it is present, and it stays present for the rest of that day and the next. At noon IST the Moon is 1.43 degrees past Ketu - the margin - having covered that distance in a little over two hours.

So two people born that morning, at 09:30 and at 09:50, get opposite answers, and both answers are correct for their own moment. A birth time recorded as "around half past nine" cannot settle it. This is the situation the calculator's margin row exists for: it shows a 09:50 birth that its yes rests on a margin of a few tenths of a degree, set by the Moon, and therefore on the accuracy of the birth time.

The same verdict appears in the dosha list of your full kundali and of the Mangal Dosha calculator, which take their verdict from the same function this calculator runs rather than keeping a second copy of the rule.

Run it with the Kaal Sarp calculator. If the answer is yes, read the margin and the graha that sets it before anything else; if the result says the true node would flip it, treat the chart as a genuine borderline case, as the calculator does.

Is Kaal Sarp Dosha in Brihat Parashara Hora Shastra?

No. A search of the BPHS translations, Saravali, the Bhrigu Sutras, Daivajna Vallabha and Advanced Predictive Astrology finds no spelling of Kaal Sarp in any of them. The Sarpa Yoga in BPHS Ch. 35 is a different rule, about malefics in the angular houses.

How common is it?

About 7.4 per cent of days from 1970 to 2014, at noon IST. But it comes in runs of up to about two weeks, in seasons, and in 22 of those 45 years it never occurred at all at noon.

Why does the calculator not tell me my type?

The twelve named types and the Kaal Amrit label come from popular practice, not from any text in this app's library. Printing them would present general knowledge as sourced. The direction - Rahu to Ketu, or Ketu to Rahu - is given as a plain fact instead.

My margin is under one degree. Do I have it or not?

By this engine's rule, yes. But one degree is within the range that a true-node calculation, or a different ayanamsa or ephemeris, could move. The calculator tells you if the true node would flip it; if not, the result is close but stable on the engine's own terms.

Does it need my birth place?

No. The verdict uses only longitudes, so a date and time are enough; without a place the time is read as India Standard Time. A resolved place adds the houses of Rahu and Ketu to the description.

Can I gain or lose it later in life?

Not in the birth chart, which is fixed at the moment of birth. The same arrangement does recur in the sky, in seasons of about two weeks at a time, but this app does not read it as a transit and attaches no meaning to its recurrence.

Is a chart in the middle of a long run a "stronger" case?

No. The engine has no strength scale for it. The only graded quantity it reports is the margin, and a wider margin makes the yes more certain, not heavier. Where in a run a birth falls is not something the calculator reports or reads.

Why might another app disagree?

It may use the true node rather than the mean node, count a graha on the axis as inside, use a different ayanamsa or ephemeris, read the birth time in a different zone, or report a "partial" form this engine does not compute. On a chart with a wide margin, none of these should change the answer.

Is there anything I need to do about it?

This app attaches no remedy to it, because it predicts no outcome. It reports a geometric fact about your chart and how close that fact was.