Free Birth Chart Calculator With Rising Sign and Houses

How to use it

1. Enter your birth date. Any year from 1800 to 2100 works.
2. Enter the time from your birth certificate, as it read on the local clock. You do not need to adjust for daylight saving time; the calculator does that.
3. Pick your birthplace. For 79 major cities the calculator uses your browser's built-in time zone database, which includes historical daylight saving rules. If your town is not listed, choose "Other place" and enter its latitude, longitude and the UTC offset in force at your birth (for example −4 for US Eastern Daylight Time).
4. If you don't know your time, tick "I don't know my birth time". You will still get your Sun and planet signs, calculated for noon, but no rising sign or houses.

The result shows the Sun, Moon and rising sign first, then a chart wheel and a table of every position, a count of elements and modalities, and a short description of your big three. The line under the headline shows the exact moment used in Universal Time (UT). If that looks wrong, the time zone is usually the reason.

What the calculator computes

For the moment you enter, the calculator works out:

• The ecliptic longitude of the Sun, Moon and eight planets, geocentric and apparent (corrected for light travel time and aberration), measured along the true ecliptic of that date. That longitude, from 0 to 360 degrees, is converted to a sign and degree: 0 to 30 is Aries, 30 to 60 Taurus, and so on.
• Retrograde motion, by checking whether each planet's longitude a day later is smaller.
• The ascendant and midheaven, from local sidereal time, your latitude and the tilt of Earth's axis on that date. The standard formula is: ascendant = atan2(cos RAMC, −(sin RAMC × cos ε + tan φ × sin ε)), where RAMC is local sidereal time in degrees, ε the obliquity of the ecliptic and φ your latitude.
• Whole sign houses: the sign of the ascendant is the first house, and each following sign is the next house.

Planet and Moon positions come from Astronomy Engine, an open-source library by Don Cross released under the MIT license. It uses a trimmed version of the VSOP87 planetary theory, a Moon model that goes back to E. W. Brown's lunar theory by way of Montenbruck and Pfleger's Astronomy on the Personal Computer, and is built to stay within one arcminute of the US Naval Observatory's NOVAS software.

How we checked it

Before publishing, we calculated five test charts (London 1990, New York 1985, Sydney 1970, Los Angeles 2001 and Denver 2026) and compared every position with NASA JPL's DE421 ephemeris, independently computed, and with a spot check in JPL's Horizons system. The largest differences were:

Both results are correct for their inputs, and that is the point of the example: the hour of daylight saving moves the Moon by about half a degree and the ascendant by several degrees.

Limits and good practice

• Birth time accuracy matters most. The ascendant moves about one degree every four minutes on average.
• Old records. Before standard time zones (the 1880s in many countries), places used local mean time. Your browser's database handles this for listed cities, but for very old dates small offsets are possible.
• Polar latitudes. Above the Arctic and Antarctic circles the ascendant behaves strangely and astrologers disagree about it, so the calculator does not show houses there.
• This is astronomy plus tradition. The positions are real; what they mean is astrological tradition, offered for reflection and entertainment.

Read how birth charts work for a guide to reading your result.

Common questions

Where do I find my birth time?

A birth certificate or hospital record usually has it. In some places only the long-form certificate lists the time. Family memories are a reasonable fallback, but note that a guess of 'around noon' can change your rising sign.

Why does my rising sign differ from another website?

Usually because of a different birth time, a time zone or daylight saving error, or a different house system. Check that the calculated UT time shown under your result looks right.

Do you store my birth details?

No. The calculation runs in your browser and nothing is sent to us or saved.