Full chart wheel
Planets in their signs and houses, with the cross-axis (Ascendant–Descendant, MC–IC) drawn. Aspect lines optional.
Cosmogram
Natal charts computed in your browser.
A natal chart calculator with the precision of a research tool and the manners of a private app. Birth date, time, place — wheel, planets, houses, aspects, and a synthesis of where the chart leans. Nothing leaves the tab.
Live
Why this exists
Most natal-chart sites are content marketplaces with a chart calculator bolted on the side. Ads, paywalls, mailing lists, accounts, "your full reading for £29" — and behind it all, your birth data quietly logged in someone else's database.
Cosmogram is the calculator without the marketplace. It uses the same Moshier ephemeris implementation that professional astrology software ships with, runs the entire computation in your browser, and writes none of your data anywhere we can see. The wheel is sharp, the tables are complete, the synthesis is plain English.
It is for serious astrology students, casual chart-curious readers, professionals who want a quick second source, and anyone who is tired of giving up their birth time to read it back to themselves.
How it works
You enter your birth date, the time as accurately as you have it, and the city. Cosmogram resolves the city to coordinates and timezone, then runs the Moshier ephemeris in JavaScript to compute planetary positions for that exact moment. The chart wheel, planet table, house table, aspect grid, and synthesis are all rendered from those numbers, in your tab.
You can switch zodiac (tropical / sidereal), house system (Placidus, Koch, Whole Sign, Equal, Campanus, Regiomontanus, Topocentric), and aspect set on the fly. Every change recomputes locally — there is no API call to wait for, no rate limit, and no logging of who read what chart.
Privacy in one paragraph
Birth data — date, time, city — is the most sensitive personal information an astrology tool handles, and Cosmogram does not transmit it anywhere. The geocoding lookup uses a public, anonymous service and only sends the city name, not your identity or the chart context. Everything else is local. Refresh the page and the data is gone, unless you've explicitly saved it to your browser.
What's in the chart
Everything you'd expect, nothing you'd resent.
Configurable
Tropical or sidereal. Seven house systems. Major and minor aspects. Switch on the fly; the chart recomputes instantly.
Detailed tables
Planets, houses, points (Chiron, lunar nodes, Lilith), aspect grid — all numbers, no fluff, copy-friendly.
Synthesis
Sign / element / modality distribution and a synthetic dominant — what the chart leans into, in plain English.
City autocomplete
Type the place; coordinates and timezone resolve automatically. Historical timezones handled correctly for older birth dates.
Copyable export
Pull the analysis as Markdown for your notes. Print the chart wheel directly from the browser.
Things people ask before they trust the chart.
Astrology earns trust by being precise about what it does and does not claim. Same here.
A snapshot of the sky at the moment you were born, drawn as a wheel divided into twelve houses. The positions of planets, the rising sign, and the angles between them are read together as a portrait of dispositions and tendencies in Western astrological tradition.
Nowhere outside your browser. Cosmogram does every calculation locally with a Moshier ephemeris implementation in JavaScript — your birth date, time, and location are not uploaded to any server. Refresh the page and the data is gone.
The Moshier ephemeris is precise to within an arcsecond for the modern era, well below the resolution of any house system. For research-grade work, professional astrologers cross-check against Swiss Ephemeris; the difference is negligible for chart interpretation.
Placidus is the modern Western default and the right choice unless you've been taught otherwise. Whole Sign is preferred in Hellenistic and Indian-influenced traditions; Koch is popular in German-speaking schools. The chart wheel updates instantly when you switch.
Tropical is the standard in Western astrology and what most readers expect. Sidereal aligns with the visible constellations and is used in Vedic and some Western evolutionary schools. Pick whichever matches the tradition you're working from.
Not yet — Cosmogram is a focused natal-chart tool. Transit overlays, synastry (chart-vs-chart), and progressions are obvious next steps; if a particular feature would unblock your work, write to us.
Drop in a date. Read the chart.
Birth date, time, place — that's all it needs. No account, no upload, no marketing list. The whole calculation is yours.