Astro.com vs Astro-Seek: Which Free Birth Chart Calculator Should You Use?
Astro.com and Astro-Seek both calculate a full birth chart for free from date, birth time and place, and on the same birth they agree to the minute of arc: for 15 August 1992 at 14:20 in New York, both put the Sun at 23°09' Leo and the Moon at 18°35' Pisces. The differences are practical. Astro.com asks for a free user profile with an email address before it shows the drawing; Astro-Seek shows the whole chart without an account. Astro-Seek opens a house menu with 40 entries, Placidus preselected; Astro.com is the home of the Swiss Ephemeris, the calculation library much of the field runs on. The Cosmic Patterns calculator is the third option when the wheel and a written reading should sit in the same place.
Checked 23 September 2026 with the same test birth on all three tools. Every link goes to the official page.
Astro.com: the reference site, behind a free profile
What it offers: Astrodienst's site calls itself one of the largest astrology portals on the web. Its free horoscopes overview lists the chart drawing, the AstroClick Portrait and a Personal Portrait excerpt beside paid reports by Liz Greene, Robert Hand and other authors, and the birth data entry uses an atlas with hospital-level coordinates: New York alone returns 13 entries. Underneath sits the Swiss Ephemeris, developed by Astrodienst on NASA's JPL planetary data, first released in 1997, on DE431 since February 2014 and on DE441 since May 2026.
How the free chart works: The entry form takes first name, gender, date, hour with an explicit unknown option, minute, country and town; the atlas resolves the place and the time zone automatically. After that step the site asks for a free user profile with a valid email address, and the chart drawing is displayed once the profile exists. In our check as a guest, no chart appeared before registration.
Best for: Difficult inputs (an old date, a small town, a time zone question), the reference ephemeris, and the depth of the Astro Shop reports if a printed study is wanted later.
Trade-off: The email step comes before the first wheel. The chart settings and the extended chart selection live inside the profile, and the paid reports and subscriptions sit close to the free tools; it takes a moment to see which is which.
Astro-Seek: every setting, no account
What it offers: The free birth chart calculator takes date, time to the second and place, and draws the chart in the browser without a login. Its extended settings hold a house menu with 40 entries, Placidus selected by default, with Koch, Regiomontanus, Campanus, Equal, Whole Sign, Porphyry, Alcabitius and Topocentric among them, a tropical or sidereal switch with a list of ayanamsas, and adjustable aspect orbs. The result page lists every planet by sign, degree and house, names the house system used, and adds computer-generated interpretations with a note saying they are exactly that.
Best for: Switching a setting and watching what moves. Whole sign against Placidus, tropical against sidereal, orbs wider or tighter: this is the workbench. The site also carries a separate Ascendant calculator, transit and synastry calculators, and ephemeris tables from 1800 to 2100.
Trade-off: 40 house options is a lot of rope. Two charts that look different are usually two settings, not two skies, and the interpretations are assembled by rule, not written for one person. A registered account exists but is not needed for the chart.
Cosmic Patterns: the wheel, then the reading
What it offers: The free chart calculator draws the wheel from date, birth time and place: ten planets by sign and degree, the Ascendant and Midheaven, the 12 houses in whole sign with each planet's house number, and the aspect lines between them. Positions come from the open-source Astronomy Engine; for the test birth they match Astro.com and Astro-Seek to the minute of arc. The chart can be saved to your inbox, and the free Big 3 reads Sun, Moon and Rising together. Without a birth time the calculator does not guess; it sends you to the Big 3, which says which placements still need the time.
Best for: Seeing the wheel and reading it in the same place. The written Complete Birth Chart reads those same positions, $9, down from $19, one time, with personalized audio.
Trade-off: One house system, whole sign, and no menu. To flip between systems or set orbs, keep Astro-Seek open beside it. The reading is a written report, not a live consultation.
Quick Comparison
Same birth, two different houses
Take the test birth again: 15 August 1992, 14:20, New York. All three tools give the Sun at 23° Leo, the Moon at 18° Pisces and 29° Scorpio rising. Astro-Seek, in its Placidus default, puts the Sun in the 9th house and the Moon in the 4th. Cosmic Patterns, in whole sign, puts the same Sun in the 10th (Leo is the tenth sign counted from Scorpio) and the same Moon in the 5th. Nobody miscalculated. One tool asks how far the Sun had climbed past the horizon; the other asks which sign the Sun shares with the count that starts at the rising sign. Astro-Seek can show both: choose Whole Sign in its house menu and the two wheels agree house for house. The reasoning behind that switch is in Placidus vs whole sign houses.
Which one should you use?
Use Astro.com if the reference ephemeris and the option of a named author's report matter more than the email step. Use Astro-Seek if the point is to change settings and see what moves, with no account and no wait. Use the Cosmic Patterns calculator if the wheel should come with a reading in the same place: the wheel is free, the Big 3 is free, and the written chart is $9, once.
Before comparing any two of them, match the inputs: the same date, the same local clock time, the same resolved place, the same house system. For the wider field of free tools, see the best free birth chart calculators; for apps rather than sites, the best birth chart apps; for what the diagram means, how to read a birth chart. When the question is no longer where the planets are but what they have been doing in your life, that is what a written reading is for.
Both calculators are free, so nothing has to be bought to check the sky. What no calculator gives you is the sentence that makes you sit still for a moment. That has always been the reading's job.
You have just read what these tools can do. None of them has read you. Somewhere in all that comparing sits a quieter question, and it is not which app is best. It is what your own sky actually says.
Your complete birth chart reads all ten planets, the aspects your chart supports and, with your birth time, the houses where each one does its work. Not a feature list. A reading of the one chart no comparison can rank: yours. All of the sky, not one page of it.
Your Complete Birth Chart
Read your full birth chart$19$9 · Yours forever · No subscription
frequently asked
Is Astro.com or Astro-Seek more accurate?
For the same birth they agree to the minute of arc: 23°09' Leo for the Sun and 18°35' Pisces for the Moon in our test, and the Cosmic Patterns calculator gives the same positions. Astro.com runs on its own Swiss Ephemeris, built on NASA's JPL data; Astro-Seek does not name its library on the result page. Differences you see between the two are settings, house system, zodiac or orbs, not accuracy.
Do I need an account to get a free birth chart at Astro.com or Astro-Seek?
At Astro.com, yes: after entering birth data as a guest, the site asks for a free user profile with a valid email address before it shows the chart drawing (checked 23 September 2026). Astro-Seek draws the full chart without any account. The Cosmic Patterns calculator needs no account either; an email is only asked if you want the chart saved to your inbox.
Why does Astro-Seek put my Sun in a different house than Cosmic Patterns?
Because the two use different house systems. Astro-Seek preselects Placidus, which cuts the houses by rising time; Cosmic Patterns draws whole sign, where each sign is one house starting from the rising sign. In our test birth the same 23° Leo Sun sits in the 9th house at Astro-Seek and in the 10th at Cosmic Patterns. Choose Whole Sign in Astro-Seek's house menu and the two agree.
Can I get whole sign houses at Astro-Seek?
Yes. Whole Sign is one of the 40 entries in the house menu under the extended settings of the birth chart calculator, next to Placidus, Koch, Equal, Porphyry and others. Placidus is preselected, so the menu has to be changed by hand before the chart is calculated.
Does the Cosmic Patterns calculator replace Astro.com or Astro-Seek?
Not as a settings workbench: it draws whole sign houses only, with no menu for house systems, zodiacs or orbs. It replaces them if you want the wheel and a reading from the same place: the wheel and the Big 3 reading are free, and the written Complete Birth Chart reads the same positions for a one-time price, with personalized audio.
Cosmic Patterns
birth charts, Big 3, and the patterns you keep repeating.