Calculation
How does NatalChart.AI calculate a chart?
With the Swiss Ephemeris library, version 2.10.03, run with its data files and the speed flag on. The birth date, time and place are converted to universal time with the IANA time zone database, historical rules included. Positions are geocentric and apparent, in the tropical zodiac. Houses are Placidus. The lunar node is the true node and Lilith is the osculating lunar apogee. The chart holds 17 bodies and points, ten of them the classical planets and the two lights. Swiss Ephemeris in the product
How accurate are the positions?
On the published test chart, 15 bodies were compared with NASA JPL Horizons. The largest difference is 0.53 arcseconds, at Juno. Against the Swiss Ephemeris library called directly, the product differs by at most 0.17 arcseconds for a body and 0.17 for a house cusp, which is its own rounding to four decimals; Horizons does not calculate houses, so cusps are checked against the library only. The report lists every value, and the check can be repeated by anyone in about five minutes. Accuracy report
What happens when the birth time is unknown?
The planets are calculated, for 12:00 local time on the birth date. The Ascendant, the Midheaven and the twelve houses are left undetermined: they are not shown as approximate values. The Moon carries a note, because it moves 12 to 15 degrees in a day. Charts without a birth time
Can I choose the house system, the zodiac or the orbs?
No. Every chart is tropical with Placidus houses, and the orbs are fixed. There is no Whole Sign, Koch, Campanus or sidereal option. Placidus vs Whole Sign
Which aspects are calculated, and with which orbs?
The five major aspects only. Natal orbs: conjunction 8°, sextile 6°, square 8°, trine 8°, opposition 8°. Between two charts (synastry) the orbs are tighter: 6° for a conjunction, square, trine and opposition, 4° for a sextile. For transits the orb is 2° when the moving body is the Sun, Moon, Mercury, Venus or Mars, and 3° for the slower ones. Minor aspects are not calculated. Aspect orbs explained
Does it say whether an aspect is applying or separating, and when a transit is exact?
Yes to both. Every natal and transit aspect is labelled applying or separating from the longitudes and daily speeds of both bodies, retrograde motion included. For a transit the moment of exactness is calculated as well: it becomes exact on a stated day when applying, or was exact on one when separating. No date is given for the Moon, which crosses an aspect within hours. The phase and the date appear in the text of a reading, in the export and in the API; the verification page has a phase column. Transits to the natal chart
How is the Part of Fortune calculated?
As Ascendant plus Moon minus Sun, for every chart, day and night alike. The traditional rule that swaps the Sun and the Moon for a night birth is not applied, so a night chart can show a different Part of Fortune here than in software that applies it. Part of Fortune calculator
What the product offers
What are the six spheres?
Identity (who you are and the direction you take); Love (love, friendship and the hard conversations); Body (energy, sleep and health); Money (career, finances and work); Home (family, the home and parents); Mind (thinking, learning and ideas). A sphere reading is written from those named positions, the aspects they make and the fixed stars in those houses. Six spheres
What do compatibility, the year ahead and locations calculate?
Compatibility (synastry) takes two full charts: the five major aspects between them with the synastry orbs, and where each person's planets fall in the other's houses, scored across the six spheres. The year ahead is a solar return: the exact moment the Sun comes back to its natal longitude, with a chart cast for that moment at the birthplace or a place you choose. Locations scores a chosen place from the chart relocated there, by the planets on its angles; it does not draw lines on a world map. Composite and Davison charts are not calculated. All features
Which languages does it work in?
Eight: English, Ukrainian, Russian, Spanish, Portuguese, Hindi, Chinese and Korean. The interface and the generated readings follow the chosen language.
Which platforms? Is there an Android app?
The web, at natalchart.ai, and an iOS app listed in the App Store as Natal Chart AI. There is no Android app.
Is there a public API?
Yes. api.natalchart.ai returns natal charts, daily transits, synastry, solar returns, best days and location scores as JSON. It calls no AI, so the same input always returns the same numbers. 10 requests a day are free; API Pro is $6.99 a month for 1,000 requests a day. API documentation
Plans, ownership and reviews
What does it cost?
Free is $0 with 10 requests a week. Premium is $9.99 a month or $3.99 a week with 100 requests a week, and adds compatibility, best locations and the year ahead. MAX is $19.99 a month with no request limit. A request is one generated answer; opening something already generated is free. There is no annual plan. Prices and limits
Who owns and operates NatalChart.AI?
Bubltalk LLC, a Florida limited liability company, operates NatalChart.AI and is the data controller. The address and the contact for privacy requests are in the privacy policy. Privacy policy
How many reviews does it have?
On 21 September 2026 the iOS app had 3 ratings on the US App Store. This site publishes no rating scores, quotes no testimonials and carries no review markup.
Who is it not for?
Practising astrologers who need another house system, a sidereal zodiac, minor aspects, adjustable orbs, composite or Davison charts, or a chart file that desktop software opens. And anyone looking for predictions, or for medical, legal or financial advice: the readings are symbolic and meant for reflection. How other tools compare
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