Rahu Ketu Calculator
Find your natal Rahu (north node) and Ketu (south node) from your birth date alone. The tool computes the mean lunar node astronomically, then gives each node’s sign, degree, nakshatra and pada in Lahiri sidereal or tropical zodiac, with the ayanamsa and the full formula printed under the result so you can check the arithmetic yourself.
Uses the mean lunar node. The true node can differ by up to about 1.5 degrees; for chart-critical precision use a full ephemeris. For entertainment and study.
Quick Answer
For a birth on 15 June 1990, Lahiri sidereal gives Rahu in Capricorn 15.97°, Shravana pada 2 and Ketu in Cancer 15.97°, Pushya pada 4. Switch the same date to tropical and Rahu moves to Aquarius 9.69°: the difference is the 23.72° Lahiri ayanamsa for that date, nothing else. Enter your own birth date above for the same readout.
Key takeaways
- Rahu and Ketu are one axis, not two separate placements: Ketu is always Rahu plus exactly 180°.
- The birth date does nearly all the work. The nodes move about 3 arc-minutes a day, so the optional birth time shifts the degree by hundredths, not the sign.
- Lahiri sidereal and tropical answers for the same birth differ by the ayanamsa alone: 23.72° in June 1990, 24.23° in October 2026.
- This is a mean-node tool. The true node can sit up to about 1.5° away, which only matters within a day or two of a sign or nakshatra boundary.
- Quick Answer
- How to use the Rahu Ketu calculator
- Worked example: 15 June 1990, checked against this exact tool
- How the calculation works: Julian day, mean node, ayanamsa
- What Rahu and Ketu are: two ends of one axis
- Mean node vs true node: the honest 1.5 degree limit
- What competing calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the Rahu Ketu calculator
Three inputs, one of them optional, and the results stay hidden until you click Calculate.
- Enter your birth date. The worked example, 15 June 1990, is pre-filled so you can reproduce the numbers here first.
- Add a birth time only if you know it. Blank means noon. A time moves the result by a few hundredths of a degree (16.00° at 00:00 versus 15.95° at 23:59 for the example date), because the nodes regress slowly. The tool uses the typed time as-is, with no timezone conversion, so enter the time as it was recorded for the birth.
- Pick the zodiac system. Sidereal (Lahiri ayanamsa) is the Vedic convention; tropical is the Western one. Run both if you want to see the ayanamsa gap directly.
- Click Calculate. You get Rahu and Ketu with sign, degree, nakshatra and pada, the system and ayanamsa used, and the formula line with both longitudes in degrees.
Worked example: 15 June 1990, checked against this exact tool
The pre-filled example returns Rahu in Capricorn and Ketu in Cancer in Lahiri sidereal, and the same axis swings a full sign in tropical. Every number below is a tool output, not a rounded retelling.
15 June 1990, noon default
309.69° tropical
309.69° − 23.72° = 285.97°
Capricorn 15.97° / Cancer 15.97°
| Run | Rahu | Ketu | Ayanamsa |
|---|---|---|---|
| 15 Jun 1990, Lahiri | Capricorn 15.97°, Shravana pada 2 | Cancer 15.97°, Pushya pada 4 | 23.72° |
| 15 Jun 1990, tropical | Aquarius 9.69°, Shatabhisha pada 1 | Leo 9.69°, Magha pada 3 | none |
| 1 Jan 2000, Lahiri | Cancer 11.19°, Pushya pada 3 | Capricorn 11.19°, Shravana pada 1 | 23.86° |
| 24 Oct 2026, Lahiri | Aquarius 2.24°, Dhanishta pada 3 | Leo 2.24°, Magha pada 1 | 24.23° |
The 1990 result also matches the historical record: the mean node sat in sidereal Capricorn from late September 1989 to mid-April 1991, so any birth in that window must show a Capricorn Rahu in the Lahiri system. A result in any other sign for a 1990 birth is a red flag about the tool, not about your chart.
How the calculation works: Julian day, mean node, ayanamsa
The tool converts your birth date to a Julian day, applies the standard mean-node polynomial, and subtracts a linear Lahiri ayanamsa for the sidereal reading. Three steps, all printed under your result.
Step 1, Julian day. The date (plus the birth time, or noon if blank) becomes a Julian day number with the standard Gregorian calendar conversion. Step 2, mean longitude of the ascending node: Ω = 125.04452° − 1934.136261° × T, where T is Julian centuries from J2000 (1 January 2000). That Ω is Rahu’s tropical longitude. Step 3, sidereal correction: for the Lahiri system the tool subtracts an ayanamsa of 23.855° + 1.397° × T. It is a linear approximation of the Lahiri value, good to a few hundredths of a degree across modern birth dates: it gives 23.72° for June 1990 and 24.23° for October 2026.
Ketu needs no formula of its own: Ketu = Rahu + 180°, wrapped back into 0–360°. The sign is the 30° block the longitude falls in, the nakshatra is the 13°20′ block, and the pada is the 3°20′ quarter of that block. If you want the full chart context around these two points, the vedic calculator computes the Moon’s own position, rashi and dasha data alongside the nodes.
What Rahu and Ketu are: two ends of one axis
Rahu and Ketu are the lunar nodes: the two points where the Moon’s orbit crosses the ecliptic. They are mathematical points, not physical bodies, which is why tradition calls them shadow planets (Chhaya Grahas).
NASA’s eclipse pages describe the same geometry from the astronomy side: the Moon’s orbit is inclined about 5.1° to the ecliptic, it crosses at two nodes, and eclipses can only happen near them. The nodes regress westward by about 19.3° per year, which is the same motion this calculator’s polynomial produces: 1934.136261° per century is 19.34° per year. In astrological reading, Rahu (the north or ascending node) is associated with ambition, appetite and the unconventional, and Ketu (the south or descending node) with detachment, the past and the spiritual. Read them as a pair: whatever Rahu intensifies in one sign and house area, Ketu loosens in the opposite one.
The sidereal framing matters here. A sidereal zodiac calculator shows the same ayanamsa shift applied to the Sun, and a full sidereal birth chart calculator places every planet in the Lahiri frame this tool uses for its Vedic mode.
Mean node vs true node: the honest 1.5 degree limit
This calculator uses the mean node, a smoothed position that regresses at a steady rate. The true node is the actual crossing point on a given day, and it wobbles around the mean by up to about 1.5° as solar gravity perturbs the Moon’s orbit.
That gap sounds large until you put it against the outputs. A sign spans 30° and a nakshatra spans 13°20′, so a 1.5° wobble changes the sign only for births within roughly a month of an ingress, and the pada only near a pada edge. Most published transit calendars and ingress dates use the mean node, so this tool reproduces those dates exactly. If your result lands within 1.5° of a sign or nakshatra boundary and the placement is chart-critical, confirm it with a full ephemeris that offers a true-node option, and say which node type any reading is based on. Mixing a mean-node Rahu with true-node transits is a quiet source of contradictory readings.
What competing calculators miss
The pattern across the top results for this keyword is more tool than this page needs and less checking than it deserves.
- Full-chart engines (Astro-Seek, Kendraya-style chart tools): precise ephemerides, but they demand birth time and birthplace and bury the two node placements inside a complete chart. If all you need is your Rahu and Ketu sign, that is ten inputs for a two-line answer.
- A rival worked example with the nodes swapped: one popular Rahu Ketu page illustrates 15 August 1990 with Rahu in Cancer and Ketu in Capricorn. Run that date here and the axis is the other way round: Rahu Capricorn 12.75° in Shravana, Ketu Cancer 12.75° in Pushya. The 1989–1991 Capricorn ingress window confirms Capricorn is the Rahu side. An example that swaps the nodes teaches the wrong axis.
- Placeholder examples (Neo Calculators-style): a worked example that prints “~XX°” as the Rahu position and labels its own sign and nakshatra as “(example)” verifies nothing. Every number here was produced by the tool above and can be reproduced in seconds.
- Transit-only tools: they tell you where the nodes are today, which answers a different question. Natal placements need your birth date, and the roughly 18-month sign cycle means a transit answer is wrong for almost every birth year.
- The gap this page fills: date-only input, both zodiac systems on one screen, the ayanamsa and longitudes printed with the result, and an explicit mean-node limit instead of silent precision claims.
Frequently asked questions
Enter your birth date, leave the birth time blank unless you know it, pick Lahiri sidereal for a Vedic reading or tropical for a Western one, and click Calculate. For 15 June 1990 in Lahiri sidereal the answer is Rahu in Capricorn and Ketu in Cancer, because the two nodes are always exactly opposite each other.
They are the two points where the Moon’s orbit crosses the ecliptic, the Sun’s apparent path. Two crossing points of two great circles are geometrically opposite, so the nodes sit 180 degrees apart by definition. That is why this calculator adds exactly 180 degrees to Rahu to get Ketu.
Use Lahiri sidereal for Vedic astrology and tropical for Western astrology. The two systems currently differ by the ayanamsa, 24.23 degrees in October 2026, which is enough to move a node into the neighbouring sign: the 15 June 1990 example is Capricorn in Lahiri sidereal and Aquarius in tropical.
No, not for the sign. The mean node moves only about 3 arc-minutes per day, so the date alone settles the sign and nakshatra except within a day or so of a boundary. The time only refines the degree: for 15 June 1990 the tool gives 16.00 degrees at 00:00, 15.97 degrees at noon and 15.95 degrees at 23:59, all in Capricorn.
A nakshatra is one of 27 lunar mansions dividing the zodiac into spans of 13 degrees 20 minutes each. A pada is one quarter of a nakshatra, 3 degrees 20 minutes wide, so the full zodiac holds 108 padas. The calculator reports the nakshatra and pada containing each node, for example Shravana pada 2 for the worked example’s Rahu.
The mean node is a smoothed average position that regresses steadily; the true node is the actual crossing point, which wobbles around the mean by up to about 1.5 degrees as the Sun perturbs the Moon’s orbit. This calculator uses the mean node, the convention behind most published transit and ingress calendars. Sign placements agree with the true node except very close to a sign boundary.
About 18 months per sign. The nodes move backward (retrograde) through the zodiac at roughly 19.3 degrees per year and complete a full circuit in about 18.6 years, a regression rate NASA’s eclipse pages give as well, since eclipses can only occur near the nodes.
No. Your Moon sign is the sign the Moon itself occupied at your birth; Rahu and Ketu are the two lunar nodes, separate mathematical points that do not depend on the Moon’s sign. Transit readings are often judged from the Moon sign, but that is a different calculation from the node positions this tool returns.
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References
- Fred Espenak, NASA Goddard Space Flight Center. Periodicity of Lunar Eclipses (the Moon’s orbit crosses the ecliptic at two nodes; the nodes regress westward by 19.3° per year; eclipse seasons). Accessed October 24, 2026.
- Fred Espenak, NASA Goddard Space Flight Center. Periodicity of Solar Eclipses (nodal geometry and the 173.3-day interval between eclipse seasons). Accessed October 24, 2026.
- Astrodienst AG. Swiss Ephemeris: General Documentation (mean node and true node as separate ephemeris points; Lahiri ayanamsa definition and its comparison with the Indian Astronomical Ephemeris). Accessed October 24, 2026.
- Encyclopaedia Britannica. Lunar Mansion (the nakshatra system as the Indian form of the lunar mansions dividing the ecliptic). Accessed October 24, 2026.
- Fred Espenak, NASA Goddard Space Flight Center. Five Millennium Catalog of Lunar Eclipses: Index (the ascending and descending nodes as the two intersection points of the lunar and terrestrial orbits). Accessed October 24, 2026.
- Jean Meeus. Astronomical Algorithms, 2nd edition, Willmann-Bell, 1998 (source of the mean longitude of the Moon’s ascending node polynomial used by this calculator). Book reference; publisher catalogue entry accessed October 24, 2026.