For developers · REST API
Precision, served — one sub-arcsecond call away.
120 REST endpoints computed against NASA JPL DE440 — natal charts, transits, synastry, astrocartography, Human Design, BaZi. Clean JSON in, exact positions out. No approximations, no license traps.
Powers ELA Map — a full locational-astrology and Human Design platform — in production.
- REST endpoints
- 120
- REST endpoints
- precision (JPL DE440)
- Sub-arcsecond
- precision (JPL DE440)
- of coverage (1550–2650)
- 1,100 yrs
- of coverage (1550–2650)
Capability grid
120 endpoints across 8 domains
Western, Vedic, Chinese, and astronomical traditions — all in one authenticated API. No license traps.
Natal & Chart
- Full natal chart with aspects, dignities, and lots
- 7 house systems (Placidus, Whole Sign, Koch, Equal…)
- Vedic / sidereal charts with nakshatra placements
- Chart rendering (SVG / PNG wheel output)
Predictive & Timing
- Transit forecasts with exact aspect windows
- Secondary progressions & solar arc directions
- Solar and lunar returns
- Electional window search
Relationship
- Synastry overlay (two-chart comparison)
- Composite (midpoint) charts
- Davison relationship chart
Astrocartography
- Planetary power lines (ASC/DSC/MC/IC)
- Crossing and paran analysis
- Local space lines and relocation charts
Human Design
- Full bodygraph computation
- Type, strategy, authority, definition
- Gates, channels, and incarnation cross
Chinese Astrology (BaZi)
- Four Pillars natal chart
- Ten Gods, luck pillars, annual pillar
- Element balance & compatibility analysis
- 24 Solar Terms
Calendar & Astronomical
- Lunar phases, void-of-course, eclipses
- Planetary hours & planetary days
- Ingresses, stations, retrograde windows
- Fixed star positions (major Ptolemaic stars)
AI & Developer Tools
- LLM-optimised response format (50% fewer tokens)
- MCP server for Claude, ChatGPT, Cursor & more
- Timezone resolution from coordinates
- OpenAPI spec for Postman/Insomnia import
Connect the MCP server in 30 seconds
Give Claude, ChatGPT, Cursor, or any MCP client live sub-arcsecond astrological data — no API key required to connect.
Technical specs
NASA-grade precision, developer-grade DX
Every position is computed from JPL DE440 — the same ephemeris NASA uses for deep-space mission planning. No approximations, no lookup tables.
Read the full developer guide →Pricing
Start free. Scale when ready.
150 free credits to start — no credit card. Wallet top-ups from $5, subscriptions from $29/mo ($22/mo billed annually).
Open Ephemeris Pro — $29/mo | Leading Credit API $19/mo | Leading REST API $11/mo | |
|---|---|---|---|
| Monthly price | $29 | $19 | $11 |
| Included credits / calls | 75,000 | 100,000* | 5,000 |
| Credits per standard chartⓘ | 1 | 500 | 1 |
| Actual charts includedⓘ | 75,000 | ~200 | 5,000 |
| True cost per chart | $0.0004 | $0.0950 | $0.0022 |
| Predictive charts includedⓘ | 15,000 | ~125 | 0 |
| Compute engine | JPL DE440 | Swiss Ephemeris | Static lookups |
| LLM-optimized output | ✓ format=llm | ✗ | ✗ |
| Overage policy | Opt-in, capped | Hard 429 crash | Hard 429 crash |
Monthly price
OE
$29
Credit API
$19
REST API
$11
Included credits / calls
OE
75,000
Credit API
100,000*
REST API
5,000
Credits per standard chart
OE
1
Credit API
500
REST API
1
Actual charts included
OE
75,000
Credit API
~200
REST API
5,000
True cost per chart
OE
$0.0004
Credit API
$0.0950
REST API
$0.0022
Predictive charts included
OE
15,000
Credit API
~125
REST API
0
Compute engine
OE
JPL DE440
Credit API
Swiss Ephemeris
REST API
Static lookups
LLM-optimized output
OE
✓ format=llm
Credit API
✗
REST API
✗
Overage policy
OE
Opt-in, capped
Credit API
Hard 429 crash
REST API
Hard 429 crash
* “100,000 credits” at a competitor typically yields ~200 basic charts due to 500-credit penalty pricing per chart. OpenEphemeris: 1 standard chart = 1 credit. Predictive operations (transits, returns) cost 5 credits each. Astrocartography costs 10 credits. All numbers based on publicly listed pricing as of March 2026.
Frequently Asked Questions
How many endpoints does this astrology API have?+
120 production REST endpoints covering Western natal, predictive (transits, progressions, returns), synastry, astrocartography, Human Design, Chinese BaZi, Vedic/sidereal, and astronomical calendar systems.
What house systems are supported?+
Seven house systems: Placidus, Koch, Porphyry, Regiomontanus, Campanus, Equal, and Whole Sign. Specify the house_system parameter on any natal chart endpoint.
Can I use this for Vedic (sidereal) astrology?+
Yes. All natal chart endpoints support sidereal positions via the ayanamsa parameter. Lahiri (Chitrapaksha), Raman, and Krishnamurti (KP) ayanamsas are supported. Vedic-specific endpoints include nakshatra placements.
Does this API support astrocartography?+
Yes. The astrocartography endpoints compute planetary power lines (ASC, DSC, MC, IC) for any natal chart, crossing analysis, paran lines, and local space lines. Available on the Pro plan and above.
Is there an LLM-optimised response format?+
Yes. Pass format=llm to any natal chart endpoint and the response is compressed to roughly half the tokens of the standard JSON format. A full natal chart fits in approximately 600 tokens instead of 4,000–8,000, which means faster and cheaper LLM inference.
Can I connect this to Claude, ChatGPT, or other AI assistants?+
Yes. The OpenEphemeris MCP server gives Claude, ChatGPT, Cursor, Windsurf, Gemini CLI, and any MCP-compatible client access to 92 astrological tools. Install via npx @openephemeris/mcp-server or connect directly to the Streamable HTTP endpoint at mcp.openephemeris.com/mcp. Full setup guide at openephemeris.com/astrology-mcp.
Is there a free trial?+
Yes — a one-time grant of 150 free trial credits, no daily cap. A natal chart costs 1 credit. No credit card required to start. Sign up and get your API key immediately. Top up anytime from $5 — credits never expire.
How accurate is the planetary data?+
The Sun, Moon, planets, and core asteroid kernel are computed from NASA JPL Development Ephemeris DE440 — the same data source used for deep-space mission planning — with sub-arcsecond precision across the full 1550–2650 CE range. The extended catalog (trans-Neptunian objects, centaurs, and additional asteroids) uses per-body JPL Horizons kernels with the same sub-arcsecond precision for 1600–2200 CE.
One API key. Every calculation.
150 free trial credits — no card required. Top up anytime from $5.
New to astrology APIs? Read our developer guide
Connect the MCP server in 30 seconds
Give Claude, ChatGPT, Cursor, or any MCP client live sub-arcsecond astrological data — no API key required to connect.