Free Birth Chart Calculator

Written by Orbitarot · Sources: our own engine, positions checked against NASA JPL Horizons (method); place data GeoNames (CC BY 4.0); interpretations our own · Updated October 16, 2026

What a birth chart shows

A birth chart, also called a natal chart, is a map of the sky drawn for one moment and one place: the moment you were born, seen from your birthplace. It answers three questions for each body. Which sign was it in (its position along the zodiac)? Which house was it in (where it stood relative to your local horizon)? And which aspects did it make (the angles it formed with the other bodies)?

The sign part depends only on the date and, for the fast Moon, the hour. The house part depends on the exact time and place, because Earth turns a full circle every day and carries every sign across the horizon. That is why two people born on the same day in different cities usually share planet signs but not a rising sign or houses.

Astrology is a symbolic tradition. Astrologers read the chart as a language of themes, not as a forecast, and nothing on this site predicts health, money, legal matters or how long anyone lives.

How the calculation works, with an example

1. Local time to Universal Time. Say you were born at 7:30 in the morning on 14 July 1995 in Chicago. In July 1995 Chicago was on daylight saving time, five hours behind Universal Time, so the moment is 12:30 UT. We read the offset from the time zone history built into your browser, so you never have to look it up.
2. Planet positions. For that moment the engine computes the ecliptic longitude of the Sun, Moon, planets, Chiron, the lunar nodes and Black Moon Lilith, in the tropical zodiac where 0 degrees Aries is the March equinox. On that date the Sun sits in the early twenties of Cancer.
3. Angles and houses. From the time and Chicago's latitude and longitude we find the Ascendant (the degree rising in the east) and the Midheaven, then divide the sky into twelve houses with the Placidus system by default. You can switch to Whole Sign or Equal houses.
4. Aspects. We measure the angle between every pair of bodies and list the conjunctions, sextiles, squares, trines, oppositions and quincunxes that fall within the orbs published on the method page.

Each step can be repeated by hand or with any ephemeris, and the method page explains how we checked the engine against NASA JPL data.

Reading your chart: where to start

A full chart has more than a hundred pieces of information, so most astrologers start with a short list.

• The big three: your Sun, Moon and rising sign. The sun, moon and rising calculator shows only these three, with a short reading of each.
• Element and modality balance: how many placements fall in fire, earth, air and water signs, and in cardinal, fixed and mutable signs. A chart with five or six placements in one element is usually read as leaning strongly on that style.
• Tight aspects: the closer an aspect is to exact, the more weight it is usually given. An aspect within 1 degree tends to be read before one at the edge of its orb.
• Angular planets: a planet close to the Ascendant or Midheaven is traditionally read as prominent in the whole chart.

Single placements have their own pages: Moon sign, rising sign, Venus sign, Mars sign, Midheaven and the others listed on the astrology hub.

Common mistakes that change a chart

• A rounded or remembered birth time. The rising sign moves through the whole zodiac in a day, about two hours per sign on average, and the house cusps move a degree every few minutes. A time remembered as "around 3" can shift the Ascendant by a whole sign. A birth certificate time is the best source you have.
• The wrong time zone or daylight saving rule. Enter the clock time written at your birth and let the place set the zone. Do not convert it to your current time zone first. The time zone database is very reliable after 1970; for earlier births in some countries, local rules were patchy, so it is worth checking the offset against a historical source.
• The wrong place with the same name. There are many cities called Springfield or San Jose. Check the country and region in the search result.
• No birth time at all. We then draw a noon chart: planet signs are still reliable (except sometimes the Moon), but the rising sign and houses are left out because they cannot be known.

Birth chart, sidereal chart and kundli

This calculator uses the tropical zodiac of Western astrology, tied to the seasons. Vedic astrology uses the sidereal zodiac, tied to the stars, which in 2026 sits about 24 degrees behind the tropical one with the Lahiri setting. That is why many people find a different Sun sign in a Vedic chart. If you want that version, use the kundli calculator, which draws a sidereal chart in the North Indian style. For two people, see the synastry chart; for the sky right now against your chart, the transit chart.

Questions

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