House Cusps Calculation via Natal Chart API

What is the House Cusps endpoint?

You need the boundary degrees of all twelve astrological houses for a given birth. The House Cusps endpoint takes birth data (date, time, place) and returns each cusp with its exact ecliptic degree, zodiac sign, and sign-relative position, plus three derived points: the Ascendant, Midheaven, and Vertex.

This endpoint is part of the Natal Chart API.

Why does this endpoint exist?

You are placing planets into houses on a wheel chart, and you need to know where each house begins. House cusps are the boundary degrees that divide the ecliptic into twelve life-area segments. Different house systems compute these boundaries differently, and the math gets thorny near polar latitudes. This endpoint handles all of that for you.

What inputs does it need?

You pass standard birth data: API key, full name, date components, time components, gender, place, decimal latitude and longitude, and timezone offset from UTC. The house_system parameter selects which calculation method to use. Authentication uses a Bearer token in the Authorization header alongside the body's api_key field.

What does the response data look like?

You get a structured object back, not a flat array. The response wraps a houses array (twelve cusp objects) plus three top-level fields for derived points: ascendant, midheaven, and vertex. Each cusp object reports the exact ecliptic position and the zodiac sign that house begins in.

The Ascendant always equals the 1st-house cusp and the Midheaven equals the 10th. They are repeated as top-level fields for convenience.

What does a real response look like?

Below is the full House Cusps response for a sample birth (24 May 2023, 14:40:43 IST, New Delhi) using the Placidus system. The Ascendant lands at 5°43' Libra, placing the chart's life-area divisions accordingly.

{
  "success": 1,
  "data": {
    "houses": [
      { "house": 1, "full_degree": "185.7194554", "sign": "Libra", "sign_no": 7, "longitude": "5:43:10" },
      { "house": 2, "full_degree": "213.9628728", "sign": "Scorpio", "sign_no": 8, "longitude": "3:57:46" },
      { "house": 3, "full_degree": "244.4181114", "sign": "Sagittarius", "sign_no": 9, "longitude": "4:25:5" },
      { "house": 4, "full_degree": "275.9631486", "sign": "Capricorn", "sign_no": 10, "longitude": "5:57:47" },
      { "house": 5, "full_degree": "307.5798285", "sign": "Aquarius", "sign_no": 11, "longitude": "7:34:47" },
      { "house": 6, "full_degree": "337.9903245", "sign": "Pisces", "sign_no": 12, "longitude": "7:59:25" },
      { "house": 7, "full_degree": "5.7194554", "sign": "Aries", "sign_no": 1, "longitude": "5:43:10" },
      { "house": 8, "full_degree": "33.9628728", "sign": "Taurus", "sign_no": 2, "longitude": "3:57:46" },
      { "house": 9, "full_degree": "64.4181114", "sign": "Gemini", "sign_no": 3, "longitude": "4:25:5" },
      { "house": 10, "full_degree": "95.9631486", "sign": "Cancer", "sign_no": 4, "longitude": "5:57:47" },
      { "house": 11, "full_degree": "127.5798285", "sign": "Leo", "sign_no": 5, "longitude": "7:34:47" },
      { "house": 12, "full_degree": "157.9903245", "sign": "Virgo", "sign_no": 6, "longitude": "7:59:25" }
    ],
    "ascendant": "185.7194554",
    "midheaven": "95.9631486",
    "vertex": "31.4160117"
  }
}

What can you build with this endpoint?

You use House Cusps to place planets into houses on every chart you render. Most natal-chart features depend on cusp data either directly (for visual placement) or indirectly (for sign-by-house interpretation logic).

1. Wheel chart house lines. Pass each full_degree to your SVG renderer to draw the twelve dividing lines on the zodiac wheel.
2. Planet-in-house assignment. Cross-reference Planetary Positions against cusps to power "Sun in the 8th house" style readings.
3. Angular emphasis. Detect planets within a few degrees of the Ascendant, Midheaven, IC, or Descendant for "angular planet" cues.
4. House-system comparison. Call the endpoint twice with different house_system values to show users how Placidus vs Whole Sign reframes their chart.

How accurate is the calculation?

You are quoting cusp degrees that down-stream interpretations will rely on, so precision matters. The House Cusps endpoint runs on Swiss Ephemeris with NASA JPL ephemeris data underneath. More than twenty house systems are exposed via the house_system parameter, with Placidus (P) as the default. Alternatives include Koch, Regiomontanus, Campanus, Equal House, Whole Sign, Porphyry, Topocentric, Alcabitius, and Gauquelin Sectors.

Quadrant-based systems like Placidus become unstable above roughly 66 degrees latitude. For polar-region births, prefer Whole Sign (W) or Equal House (E), which divide the ecliptic into clean 30-degree segments and stay reliable everywhere.

How does this relate to the parent API?

You are stitching together the spatial layout of a birth chart, and this endpoint provides the framework. This endpoint complements the Natal Chart API by providing the twelve house cusp boundaries plus the Ascendant, Midheaven, and Vertex.

Planetary Positions tells you where each body sits on the ecliptic. House Cusps tells you where each life-area boundary sits. Combine the two and you can place any planet into its correct house. The wheel chart endpoint pulls cusp data to render the twelve dividing lines.

Summary

The House Cusps endpoint returns twelve cusp boundaries plus the Ascendant, Midheaven, and Vertex for any birth datetime. It supports more than twenty house systems via a single parameter, runs on Swiss Ephemeris for arc-second precision, and pairs directly with Planetary Positions to power planet-in-house assignment. Call it whenever your chart needs a house framework.