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Free Horoscope JSON Generator for AI Astrology | Western, Vedic & Four Pillars
Create a precise horoscope from your birth data and export it as JSON to use with generative AI such as ChatGPT, Gemini, and Claude. In a single calculation this free tool produces three charts at once — a Western horoscope (Tropical zodiac / Placidus houses), a Vedic horoscope (Sidereal / Lahiri ayanamsha), and a Chinese Four Pillars (Sizhu / Bazi) chart. All calculation runs entirely in your browser, and no birth data is ever sent to a server.
Western, Vedic & Four Pillars — All-in-One Calculator
Enter your birth date, time, sex, and birthplace to instantly calculate three charts at once: a Western horoscope (Tropical / Placidus), a Vedic horoscope (Sidereal / Lahiri), and a Chinese Four Pillars (Sizhu) chart. Set your birthplace by Japanese prefecture or by latitude/longitude (worldwide).
Your input is never sent to any server and is not saved to cookies or local storage. All calculations run entirely in your browser, and your data is cleared the moment you close the page.
Algorithms & Sources
- Planetary positions: Astronomy Engine by Don Cross (MIT License). Copyright (c) 2019-2025 Don Cross. View full license.
- Solar longitude / equation of time / ΔT: Jean Meeus, Astronomical Algorithms, 2nd Ed., Ch.25 / Ch.28 / Ch.10.
- House division: Placidus (traditional iterative method).
- Ayanamsha: Lahiri (official Indian standard, per the Indian Astronomical Ephemeris).
- Vimshottari Dasha: traditional 120-year cycle (Bṛhat Parāśara Horā Śāstra tradition).
- Four Pillars stems/branches, solar terms & hidden stems: same algorithm as our Four Pillars chart calculator (in-house implementation).
- Asteroids & sensitive points (optional): Ceres, Pallas, Juno and Vesta are computed from 1-year multi-epoch osculating elements with Kepler propagation from the nearest epoch — error under 0.4 arcmin across 1900–2099 vs JPL Horizons. Chiron uses a piecewise Chebyshev fit of its heliocentric position (~0.06 arcsec, effectively matching Swiss Ephemeris). Lilith is the Mean Black Moon (lunar apogee); Vertex / AntiVertex are geometric sensitive points (ecliptic × prime vertical).
* These results are reference values based on astronomical algorithms. In professional readings, differing schools, calendar systems, and the accuracy of the birth time can significantly affect the outcome.
Three astrology systems in one JSON, ready for AI
Most apps ask only for your birth date and let the AI guess the rest. This tool instead calculates your exact planetary longitudes, houses, aspects, dasha periods, and Four Pillars, and packages them into one structured JSON file. Feeding that high-quality data to an AI lets it analyze you on a precise foundation — and combining three traditions in one file enables a genuine multi-system reading.
Read your horoscope with AI (ChatGPT / Gemini / Claude)
After you generate your chart, download or copy the JSON, paste it into your favorite AI, and ask it to interpret your love life, career, yearly outlook, or compatibility. Because the AI works from accurate astronomical data rather than guesswork, the reading is far more specific and convincing.
Ready-made prompts are available on our AI astrology prompt collection — copy a prompt for overall life, love, career, compatibility, or marriage readings, then paste it with your JSON. Want proof it works? See our blind AI readings of Steve Jobs & Princess Diana.
How to use (5 steps)
- Enter your birth date, time, sex, and birthplace. Outside Japan, choose the “Latitude / Longitude” mode and enter your coordinates (a lookup link is provided in the form).
- Click Calculate to compute all three charts at once.
- Copy or download the JSON from the result area.
- Paste the JSON into ChatGPT, Gemini, or Claude.
- Send a prompt asking for the reading you want, and the AI generates a personalized interpretation.
The three systems: Western, Vedic & Four Pillars
Western Astrology (Tropical / Placidus)
The tropical zodiac with Placidus houses — Sun, Moon, the planets, Ascendant and Midheaven, major aspects, and classical aspect patterns (Stellium, Grand Trine, T-Square, Yod, and more). Optionally you can also include Chiron and the four main asteroids (Ceres, Pallas, Juno, Vesta), plus the Black Moon Lilith and the Vertex / AntiVertex — Chiron is computed to ~0.06 arcsec and the asteroids to under 0.4 arcmin (vs JPL Horizons).
Vedic Astrology (Sidereal / Lahiri / Jyotish)
The sidereal zodiac with the Lahiri ayanamsha — Rashis, Nakshatras and padas, Vimshottari Dasha, Ashtakavarga, Shadbala, and the notable yogas of Jyotish.
Four Pillars of Destiny (Sizhu / Bazi)
The Chinese four-pillar chart — Heavenly Stems and Earthly Branches, hidden stems (three methods), Ten Gods, the Twelve Stages, luck pillars, and annual pillars, with both the Teiki and Koki solar-term methods shown side by side.
Accuracy & sources (Swiss Ephemeris-grade)
Planetary positions are computed with the open-source Astronomy Engine (MIT, Swiss Ephemeris-grade) plus Jean Meeus’ published formulae, to arc-second precision. The data is accurate enough to use as the foundation for serious AI-assisted readings.
Frequently asked questions (FAQ)
Why are my degrees, houses, or ASC/MC different from other software?
This is not a bug. Results vary with the house system, ayanamsha, time-zone handling, and rounding. This tool uses the tropical zodiac with Placidus houses for the Western chart and the Lahiri ayanamsha for the Vedic chart.
What if I don’t know my birth time?
You can still use the tool; it will compute with 12:00 noon as a fallback. Note that the Moon position, Ascendant, and the hour pillar become less accurate without an exact time.
Can it calculate charts for people born outside Japan?
Yes. Switch to “Latitude / Longitude” mode and enter your coordinates and UTC offset. A coordinate-lookup link (LatLong.net) is provided right in the form.
Why do Western, Vedic, and Four Pillars give different results?
Each tradition uses a different zodiac, calendar, and symbolic framework, so they emphasize different things. That is exactly why combining all three in one JSON lets an AI cross-reference them for a richer, multi-angle reading.
What are Rahu and Ketu?
They are the Moon’s north and south nodes (the Dragon’s Head and Tail) in Vedic astrology, treated as shadow planets with strong karmic significance.
Which “solar-term method” is correct for the Four Pillars — Teiki or Koki?
Both are valid traditions for determining the month boundary; schools differ. This tool shows both side by side so you can compare.
Why are there three hidden-stem (Zokan) methods?
Different Four Pillars schools assign the hidden stems within each Earthly Branch differently. The tool shows the monthly-division, commanding, and main-only methods so you can follow your preferred school.
What is the “required ratio” in Shadbala?
Shadbala measures the six-fold strength of each planet in Vedic astrology; the required ratio compares a planet’s total strength against the minimum considered strong.
Is my input sent to a server?
No. All calculation runs entirely in your browser, and your birth data is never sent to any server. When you use the JSON with an AI, you paste it yourself.
How do I use the resulting JSON with ChatGPT, Gemini, or Claude?
Copy or download the JSON, paste it into the AI chat, then ask for the reading you want (for example, “Based on this data, read my love life”). The JSON keys are in English so any AI can parse them.
I want to understand the meaning of each planet and point (ASC, MC, house cusps).
See our complete planet & point guide (in Japanese), which compares how Western and Vedic astrology interpret each body and sensitive point.
What is Western astrology? What is a horoscope?
Western astrology interprets the positions of the Sun, Moon, and planets along the tropical zodiac at the moment of birth. A horoscope (natal chart) is the resulting map of those positions across the twelve houses.
Can it show a bi-wheel chart or transits?
The JSON can include current transit positions (you can toggle this in the form), letting an AI discuss your current outlook in addition to the natal chart.
Privacy & notes
- All calculations run in your browser; no birth data is transmitted or stored.
- AI readings are for entertainment and reference only — do not rely on them for medical, legal, or financial decisions.
- Results are reference values based on astronomical algorithms; schools and calendar systems differ.
Related pages
- AI astrology prompts for ChatGPT, Gemini & Claude (English)
- Sample: AI reads Steve Jobs & Princess Diana — blind (English)
The following companion pages are written in Japanese.