Astro.com and Astrolium use the exact same calculation engine. Both license the Swiss Ephemeris. A chart cast in Astrolium and the same chart cast in astro.com will produce planetary positions that match to the arc-second. The comparison is entirely about chart types, workflow, and interface.
The calculation tie
Astro.com's parent company, Astrodienst, sponsored the creation of the Swiss Ephemeris in the 1990s. They still host it. Astrolium uses the same Swiss Ephemeris DE441. If you cast the same chart in both tools and compare the results, the positions will be identical.
This matters because some practitioners are skeptical of newer tools on accuracy grounds. That concern applies to tools using their own ephemeris. Neither Astrolium nor astro.com is one of those tools.
What changed in the May 2026 sprint
Astrolium shipped seven astro.com-parity additions in a single sprint: dedicated draconic and harmonic endpoints (replacing client-side approximation math), real Davison composite (not the natal-as-placeholder it was before), antiscia, heliocentric, local space, the Hamburg School / Uranian planets, all 13 Bonatti medieval lots, an electional search engine, and server-side planetary hours with multilingual interpretations.
The practical result: every chart type and technique a working practitioner reaches for in a session is now in Astrolium. The remaining astro.com advantages are research-grade.
Where astro.com still leads
The 20,000-body asteroid catalog. Astrolium ships 26 named bodies with interpretations (14 classical asteroids, 4 dwarf planets, 9 Hamburg School hypotheticals, and Transpluto). Astro.com accepts any of 20,000 minor bodies by catalogue number. For deep symbolic research — chart astrology with named celebrity asteroids, mythological work — astro.com is the right tool.
Primary directions. Marc Edmund Jones tradition uses primary directions with 3D timelines (10-year and 30-year views). Astro.com has had this for years. Astrolium ships it in 2027.
Graphic ephemeris and declination charts. Long-cycle visualization of transits as line graphs across time. Astrolium has the predictive scrubber and transit report, which solve a different problem; for graphic ephemeris specifically, astro.com remains the option.
Sidereal modes. Lahiri is the Vedic standard and Astrolium uses it. Astro.com offers nine additional sidereal modes (Krishnamurti, Raman, Fagan-Bradley, and others). For sidereal practitioners using a non-Lahiri mode, astro.com fills the gap.
AstroDatabank. The 70,000-chart celebrity database with Rodden Rating reliability codes. Hand-curated since the 1990s. Astrolium does not have an equivalent and there is no plan to build one.
Liz Greene and Robert Hand reports in 100+ languages. Astro.com's interpretation reports are paid add-ons starting around $5. They are pre-written, static, and authored by some of the most respected names in the field. For consumers who want a Liz Greene psychological reading in Spanish or Portuguese, astro.com is the right destination.
Where Astrolium leads
Zodiacal releasing. Astro.com does not offer zodiacal releasing in any form. Astrolium ships first-class ZR for both the Lot of Fortune and the Lot of Spirit, with L1 through L4 levels and a calendar overlay of period dates. For practitioners using Hellenistic timing, this alone is the reason to use Astrolium.
Bonatti's 13 medieval lots. Astro.com's Arabic parts table covers only the Hermetic 7 (Fortune, Spirit, Eros, Necessity, Courage, Victory, Nemesis). Astrolium ships all 13 Bonatti lots (Marriage, Children, Father, Mother, Siblings, Death, Disease, Travel, Property, Career, Friends, Enemies, Religion) with sect-aware formulas per Bonatti, Paulus, and Vettius Valens. For medieval and traditional practitioners, this is a hard gap closed.
Electional search engine. Astro.com's "The Best Time" is an hour-by-hour scoring tool in a 1998 CGI form. Astrolium's electional search engine scans up to 26,000 candidate moments per query across 12 activity profiles (wedding, surgery, business launch, contracts, real estate, travel, legal, agriculture, building, investment, creative launch, relocation), returns the top 10 windows graded A through F, plus a daily heatmap and excluded ranges with reason codes. The two are not in the same workflow generation.
Local space with Cozzi polar projection. Astro.com's AstroClick Local Space is a basic wheel. Astrolium uses Cozzi's tradition-correct polar projection (zenith at center, horizon as a ring, below-horizon planets in an annular band, cardinal crosshairs through center) plus 16-point compass bearings and altitude arrows. For practitioners using Cozzi's methodology for relocation work, the difference is significant.
Heliocentric as a rendered wheel. Astro.com's heliocentric output is a text data dump via a swetest CGI page. Astrolium renders a proper heliocentric wheel with Earth at the natal Sun's opposite, Sun/Moon/lunar nodes omitted (with a metadata block explaining why), and Mercury/Venus correctly shown as non-retrograde.
Firdaria as a visual timeline. Astro.com's firdaria is a text table. Astrolium ships a visual 75-year timeline with sub-periods and time-lord highlighting.
Human Design alongside Western astrology. Astro.com has no Human Design surface at all. Astrolium ships the bodygraph calculator with type, strategy, authority, and the full gate/channel chart, plus a type-and-authority compatibility view for couples work and a daily HD transit overlay for clients who track Cross of Planning or Cross of the Sphinx activations. For practitioners who weave HD into Western readings, this closes a gap astro.com has never addressed.
Astrocartography as a working stack, not a single map. AstroClick Travel renders one map and stops. Astrolium ships three additional ACG tools alongside the planetary line map: an open-ended city search that ranks 600 cities across 10 life areas for a single chart, and a head-to-head comparison that places two finalist cities side by side with line distances, parans, and life-area scores. For a relocation client weighing Berlin versus Lisbon, this is the difference between "here are your lines" and a decision-ready brief.
Client workflow. Astro.com was never built to run a practice. It casts charts; it does not remember them. Astrolium's client CRM stores every chart alongside session notes, intake forms, and tags. The predictive scrubber lets you drag to any date rather than generating a new chart. Shareable client URLs let clients open their chart on any device without logging in.
AI interpretation. Astro.com's interpretation content is high-quality but static and non-editable. Astrolium's AI assistant reads the actual chart positions, cites what it is reading from, and opens its draft in an editable markdown surface. It is not a replacement for the astrologer's reading; it is a drafting tool.
Mobile. Astro.com is a desktop CGI tool forced onto a phone screen. Every chart requires horizontal scrolling and pinch-zooming. Astrolium's interface was built responsive from day one, sub-300ms chart render on mobile data.
How to use both
Most practitioners now use astro.com as a research tool — for AstroDatabank lookups, the 20,000-asteroid catalogue, primary directions, and the multilingual Liz Greene reports when a non-English client wants the static report format. They use Astrolium as their primary working surface: casting the charts they will actually read for clients, attaching session notes, generating shareable reports, running electional searches, and working with the predictive scrubber.
For the chart types both tools cover (which is now most of them), Astrolium's mobile UX and sub-300ms response usually wins for in-session work; astro.com's brand authority and 25 years of accumulated content win for citations and research.
For the full feature list and pricing, see Astrolium features and pricing. For comparison against desktop software, see Solar Fire vs Astrolium and Astro Gold vs Astrolium. For a complete roundup, see best astrology software 2026.