The accuracy of a natal chart comes from its ephemeris, and most of these tools do not say which one they use. Four of the twelve name it outright: Astrodienst, Astro Gold, AstroMatrix and NatalChart.AI all state the Swiss Ephemeris. Astro-Seek names JPL DE431 on its ephemeris tables. Co-Star says it uses data from NASA’s Jet Propulsion Laboratory without naming a library. The remaining six say nothing about where their numbers come from, which is not evidence that they are wrong, only that you cannot check them.
The differences you can check are elsewhere, and they are larger than most comparisons admit. These tools do not agree on the house system: Astrodienst offers 23 and Astro Gold more than 25, while Co-Star uses Porphyry, The Pattern and CHANI use Whole Sign, and we use Placidus and nothing else. The same birth data gives different house placements in each. They also differ on what happens when you do not know your birth time, and on whether the interpretation tells you which placement it came from.
Astrodienst draws charts for guest users and offers 23 house systems. Astro-Seek has no paid tier at all and publishes its default orbs. NatalChart.AI, our product, computes one chart in one system, tropical and Placidus, and publishes every intermediate value of it so you can check the arithmetic against an independent ephemeris.
Who made this table
NatalChart.AI is our product and it is in this table. We did not score the tools. Every column is a property stated on the vendor’s own page, app store listing or help centre, and the links are below the table with the date we read them. Where another tool does something we don’t, such as more house systems, minor aspects, adjustable orbs or chart files for desktop software, the page says so.
“Not stated” means the vendor does not publish that property. It does not mean the tool lacks it. We did not guess, and we did not fill a cell from a review.
Twelve tools, ten properties
| Tool | Ephemeris stated | House systems | Chart without an account | No exact birth time | Interpretation | Names aspect and orb | Languages | Apps | Export | Price |
|---|---|---|---|---|---|---|---|---|---|---|
| NatalChart.AIour product | Swiss Ephemeris 2.10.03 | Placidus only | yes | computes and marks what is undetermined | AI, from the computed chart | yes, orb in degrees, with applying/separating | 8, interpretation included | iOS · web (no Android) | PDF report and chart poster on MAX · JSON through the API | free · $3.99/wk · $9.99/mo · MAX $19.99/mo |
| Astrodienstastro.com | Swiss Ephemeris (DE441 since May 2026) | 23 | yes, as a guest user | option "unknown" → assumes 12:00 noon | written reports by named astrologers | yes, with applying/separating | 12, not all content translated | web shortcut only | PDF chart drawings | free charts · PLUS $12.90/yr · PDF $39.90/yr · reports from $69.90 |
| Astro-Seek | JPL DE431 (on its ephemeris tables) | 19 | not stated | checkbox "(unknown time)"; effect not stated | reference articles by factor | yes, default orbs published | 9 | not stated | text export for further analysis | free, no paid tier |
| TimePassagesAstroGraph | not stated | 8 named on the web calculator, more on desktop | no, a free account is required | option "Unknown (Use sunrise)" → sunrise chart with solar houses | written by Henry Seltzer; "Not AI" | yes, with applying/separating | 10 (App Store) | iOS · Android · macOS · Windows | .chw · .qck · PDF · JPG · PNG · TIFF | desktop $79 to $699 one-off · Pro $7.99/mo or $59.99/yr |
| Cafe Astrology | not stated | 6 (Placidus default) | yes, no e-mail needed | checkbox "Unknown Time" → omits Moon, ASC, MC, Vertex, Part of Fortune and all house positions | written by the site's own author, Annie | yes, with a worked example | not stated | not stated | print / PDF | free reports · paid reports $2.95 to $16.00 one-off |
| Co-Star | NASA JPL data; no library named | Porphyry, tropical | no, phone or Apple account and SMS code; the web chart needs an e-mail | not stated; "if you can find out what time you were born, we can do the rest" | human astrologers working with AI | aspects listed with exact angles; orb not stated | 1 (English) | iOS · Android | not stated | free with à-la-carte purchases $2.99 to $11.99 · Pro-Star $8.99/mo |
| The Pattern | not stated | Whole Sign | web chart requires an e-mail; app not stated | option "I don't know my birth time"; effect not stated | human-written insights; In-Depth runs on own infrastructure, not third-party AI | square and opposition named by angle; orb not stated | 1 (English) | iOS · Android · web | not stated; data on request by e-mail | free · Go Deeper+ $14.99/mo · $83.99/yr |
| CHANI | not stated | Whole Sign, true nodes, Black Moon Lilith | not stated | no option; help says enter 12:00 noon, "your reading will be less precise" | states it is made by real astrologers, not AI | aspects by whole sign, not by orb; transits by degree | 1 (English) | iOS · Android · web chart tool | not stated | free tier · $11.99/mo · $107.99/yr |
| Astro Gold | Swiss Ephemeris; version not stated | 25+ | not stated for iOS/Android; licence key on macOS/Windows | not stated | built-in interpretations; author not stated | yes, editable orbs, applying/separating separately | 1 (English) | iOS · Android · macOS · Windows | .SFcht, interchangeable with Solar Fire · PDF | iOS lifetime $69.99 · Android $49.99 · macOS $249.99 · Windows $249.99 |
| AstroMatrix | Swiss Ephemeris; version not stated | 8 named | not stated | option "I don't know my birth time" → noon chart with approximate houses | assembled by the vendor's own algorithm from its text library | major aspects and configurations named; orb not stated | 1 (English) | iOS · Android | PDF (premium) | free with ads · subscriptions $2.49/mo to $14.99/yr · lifetime $24.99 to $49.99 |
| Sanctuary | not stated | not stated | not stated | not stated | live 1:1 chat with a human astrologer, tarot reader or psychic | not stated | 1 (English) | iOS · Android · web | not stated | free horoscopes and birth chart details · Sanctuary+ $14.99/mo, $49.99/yr · readings $4.99 to $49.99, per-minute $4.99 to $19.99 |
| AstroSage | not stated | house systems not stated; ayanamsa selectable: Lahiri, Raman, KP, Sayan; North/South Indian chart styles; 16 divisional charts | free kundli stated; account needed to save charts | not stated | AI astrologer chat and live astrologers | "Western aspects" listed; orb not stated | 18 (Google Play) | iOS · Android · web | PDF download, e-mail, Bluetooth | free kundli · paid plans and readings; amounts not stated |
The same cells, one tool at a time and with the sources next to each row, are on the feature matrix. The same table read for a different question, which calculator fits which situation, is on best natal chart calculators.
The same chart, three different sets of houses
House systems divide the sky differently, and the tools here do not agree on which division to use. Co-Star uses Porphyry. The Pattern and CHANI use Whole Sign. Cafe Astrology, Astrodienst, Astro-Seek, TimePassages, Astro Gold, AstroMatrix and this site default to Placidus, and the first six let you change it.
Planets do not move when you change the system: their signs and degrees are identical. What changes is which house a planet falls in, and near a cusp that can move a placement a whole house. So if two apps tell you different things about your second house, that is usually not a disagreement about astronomy. It is a disagreement about where to draw the line, and both are drawing it by a published rule.
This is worth knowing before you conclude that one of them is wrong. How two of these systems draw the line is on Placidus vs Whole Sign.
Where the other tools win
There are four places where a tool in the table does something we do not.
Astrodienst. Astrodienst offers 23 house systems to our one, and PDF chart drawings; the only chart drawing we export is the poster on the MAX plan. Its aspect tables mark whether an aspect is applying or separating and by how much. We calculate applying and separating too, and the result is in the data the reading is written from, in the downloadable test chart and in the API; the aspect list in the app has no label for it. If you already read charts, it gives you more to work with than we do.
Astro-Seek. Astro-Seek publishes its default orbs down to the arcminute, offers 19 house systems, and has no paid tier of any kind.
Astro Gold and TimePassages. Astro Gold and TimePassages are installed software. They work offline and write files other desktop programs open: Astro Gold’s .SFcht is interchangeable with Solar Fire, TimePassages exports .qck. We have no chart-file export that desktop astrology software opens. What we export is a PDF report and a chart poster on the MAX plan, and JSON through the API.
Cafe Astrology. Cafe Astrology states exactly what its report leaves out when the birth time is unknown, factor by factor. That is the same discipline we apply, and they published it first.
What NatalChart.AI does not do
We compute the five major aspects only, with fixed orbs: conjunction 8°, sextile 6°, square 8°, trine 8°, opposition 8°. There is one house system, Placidus, and one zodiac, the tropical. Tools aimed at practising astrologers add minor aspects, adjustable orbs and a choice of house system. If you work with quincunxes or Whole Sign houses, this is not the tool for that. NatalChart.AI runs on the web and on iOS; there is no Android app.
What our own row rests on
This is checkable. We publish the intermediate values of a fixed test chart, planetary longitudes to four decimal places and all twelve house cusps, next to the same values from JPL Horizons, which NASA publishes and we do not control. Across 15 bodies the largest difference is 0.53 arcseconds, and the method takes five minutes to repeat with any tool, including ours. See how to verify a chart and the accuracy report.
Calculate first. Interpret second. NatalChart.AI calculates the natal chart with Swiss Ephemeris, then uses AI to interpret the calculated placements, houses and aspects. In the table that is the Interpretation column of our row: AI, from the computed chart. Read the method →
Questions
Which natal chart calculator is the most accurate?
Accuracy comes from the ephemeris, not the interface. Any tool built on the Swiss Ephemeris computes planetary positions to better than one arcsecond for modern dates. Differences you see between such tools come from house system, time zone handling or rounding, not from the underlying astronomy. Four of the twelve tools here state the Swiss Ephemeris, Astro-Seek names JPL DE431, Co-Star names NASA JPL data, and the other six do not say.
What is the Swiss Ephemeris?
A planetary position library released by Astrodienst. Version 2.10.03, which we use, is derived from NASA's JPL DE431. Astrodienst states that since May 2026 the library is based on the newer DE441. It is the data layer under four of the twelve tools in this table, by their own statement. It is not a brand of accuracy. It is a specific dataset, and a tool either uses it or does not.
Can I get a chart without knowing my birth time?
Yes, with a limit, and the tools handle it four different ways. Astrodienst and AstroMatrix assume noon. TimePassages builds a sunrise chart with solar houses. CHANI has no option and tells you to type noon yourself. Cafe Astrology drops the Moon, the Ascendant, the Midheaven, the Vertex, the Part of Fortune and every house position, and says so. We compute the chart and mark the Ascendant and the houses as undetermined instead of approximating them. The table says which is which.
Do AI astrology tools calculate the chart or make it up?
Both kinds exist. A tool that computes the chart first and then interprets it can name the planet, the aspect and the orb it used. A tool that generates text from your sign alone cannot. Ask it which aspect a statement is based on; the answer separates the two. In this table Co-Star, The Pattern, AstroMatrix and AstroSage name aspects without stating an orb, and CHANI reads natal aspects by whole sign. NatalChart.AI states the orb in degrees.
Which tools do professional astrologers use?
We cannot measure that, so we will not claim it. What is checkable is which tools write files other professional software reads: Astro Gold's .SFcht is interchangeable with Solar Fire, and TimePassages exports .qck for the same purpose. Astrodienst offers 23 house systems and Astro Gold more than 25. We do neither.
Does NatalChart.AI let me change the house system?
No. Every chart is tropical and Placidus. If you need Whole Sign, Koch, Campanus or another system, read the house systems column: Astrodienst states 23, Astro-Seek 19, Astro Gold more than 25, TimePassages and AstroMatrix name 8 each, and Cafe Astrology offers 6.
How often is this comparison updated?
Reviewed every four months. Last check 21 September 2026, next 19 January 2027. Every row links to the page it was read from, with the date.
NatalChart.AI is in this list. Isn't that a conflict of interest?
It is, and that is why the list has no scores. Every column is a property stated on the vendor's own page, and the links are in Sources. Where another tool does something we don't, the page says so: there are four such places, and they have their own section under the table.
Sources
The vendor pages below were read on . Each row of the table comes from the vendor’s own site, app store listing or help centre, and from nowhere else.
- NatalChart.AI: natalchart.ai/verify-your-chart · natalchart.ai/llm-hub/natalchart-ai · natalchart.ai/pricing · natalchart.ai/developers, our own pages, kept current with the product.
- Astrodienst (astro.com): astro.com/faq/fq_fh_calc_e.htm · astro.com/faq/fq_fh_owhouse_e.htm · astro.com/faq/fq_de_time_e.htm · astro.com/faq/fq_ma_log_e.htm · astro.com/faq/fq_fh_legend_e.htm · astro.com/faq/fq_hp_lnav_e.htm · astro.com/swisseph/swephinfo_e.htm · astro.com/prod/pr_astroplus_e.htm · astro.com/prod/pr_pdfdraw_e.htm, read 18 September 2026.
- Astro-Seek: astro-seek.com/faq · horoscopes.astro-seek.com/birth-chart-horoscope-online · horoscopes.astro-seek.com/astrology-house-systems-calculator · horoscopes.astro-seek.com/jpl-de431-ephemeris-astrology-online-tables · horoscopes.astro-seek.com/chatgpt-ai-astrology-free-birth-chart, read 18 September 2026.
- TimePassages (AstroGraph): astrograph.com/timepassages/features · astrograph.com/timepassages/mobile · astrograph.com/birth-chart · support.astrograph.com (desktop manual) · apps.apple.com/us/app/timepassages-astrology/id488946918, read 18 September 2026.
- Cafe Astrology: cafeastrology.com/free-natal-chart-report.html · cafeastrology.com/articles/how-to-read-natal-chart-report.html · cafeastrology.com/shop/all-reports/ · astro.cafeastrology.com/natal.php, read 18 September 2026.
- Co-Star: costarastrology.com/faq · costarastrology.com/natal-chart · apps.apple.com/us/app/co-star-personalized-astrology/id1264782561, read 18 September 2026.
- The Pattern: thepattern.com/natalchart · thepattern.zendesk.com (help centre: house system, chart lines, In-Depth, data download) · apps.apple.com/us/app/the-pattern/id1071085727, read 18 September 2026.
- CHANI: chaninicholas.zendesk.com (help centre: chart calculation, aspects, unknown birth time, app pricing, free vs premium) · apps.apple.com/us/app/chani-your-astrology-guide/id1532791252, read 18 September 2026.
- Astro Gold: astrogold.io/get-astro-gold/for-ios · astrogold.io/get-astro-gold/for-android · astrogold.io/get-astro-gold/for-macos · astrogold.io/get-astro-gold/for-windows · astrogold.io/help/faqs, read 18 September 2026.
- AstroMatrix: astromatrix.org/tools/birth-chart · apps.apple.com/us/app/astromatrix-horoscopes/id1065636826, read 18 September 2026.
- Sanctuary: sanctuaryworld.co · sanctuaryworld.co/faq · shop.sanctuaryworld.co/pages/our-app · apps.apple.com/us/app/sanctuary-astrology/id1417411962, read 18 September 2026.
- AstroSage: astrosage.com/kundli · play.google.com/store/apps/details?id=com.ojassoft.astrosage, read 18 September 2026.
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