Birth Chart Calculator — Free Natal Chart with Ascendant and Houses
Calculator
Birth Chart Calculator
Your free natal chart: positions of the Sun, Moon and planets in the signs, Ascendant, Midheaven, houses and aspects
Tropical positions calculated with the astronomy-engine astronomical library; Ascendant, Midheaven and houses with the Placidus system. The time of birth is converted taking into account historical Italian daylight saving time. Aspect orbs: 8° (6° for the sextile). R = retrograde planet. The positions are astronomical; the meaning of signs, houses and aspects belongs to the astrological tradition, which is not a scientific discipline: use the birth chart for curiosity and entertainment.
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How the birth chart calculation works
The birth chart, or natal chart, is the map of the sky at the moment and place you were born: where the Sun, the Moon and the planets were along the zodiac, which point of the zodiac was rising on the horizon (the Ascendant) and how the sky was divided into the twelve houses. Enter your date, time and place of birth: the calculator draws the chart wheel, with the sign, degree and house of each planet and the main aspects.
The positions are an astronomical calculation: the real positions of the celestial bodies at that instant. The meaning attributed to signs, houses and aspects, on the other hand, belongs to the astrological tradition, which is not a scientific discipline: that is why the calculator shows the chart but offers no interpretations or predictions. The calculation runs in your browser; on first use the page downloads the astronomical library, so a connection is required.
What is calculated and with which methods
| Element | How it is obtained |
|---|---|
| Sun, Moon and planets | apparent position seen from the centre of the Earth, on the ecliptic of date, with the open source library astronomy-engine 2.1.19 |
| Zodiac signs | tropical zodiac: twelve 30° sectors starting from the vernal point (the Sun at the March equinox) |
| Ascendant and Midheaven | local sidereal time, latitude and the inclination of the Earth’s equator to the ecliptic |
| Houses | Placidus system: the cusps divide into three equal parts, in time, the diurnal and nocturnal semi-arcs of each point of the ecliptic |
| Aspects | conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°), with an orb of 8° (6° for the sextile) |
| Retrograde planet (R) | the longitude decreases over the following hour: seen from the Earth, the planet appears to move backwards |
We compared the results with Swiss Ephemeris at 400 randomly chosen instants between 1900 and 2100 in Italian locations, and with NASA’s JPL Horizons ephemerides on a few test charts: for births from 1900 to today the differences stay below one hundredth of a degree, less than the arcminute to which positions are shown. Aspect orbs, on the other hand, are a convention: other programs use wider or narrower ones.
Why the exact time and place are needed
The planets move slowly, but the Earth’s rotation brings the whole zodiac up over the horizon in about a day, and the signs do not all rise at the same speed: in Rome the Ascendant stays in Aries or Pisces for little more than an hour, while each sign from Leo to Scorpio takes about two and a half hours. That is why the Ascendant and houses change within a few minutes and depend on the point on Earth where you were born. The Moon is fast too: it travels between half a degree and two thirds of a degree every hour.
Enter the time as the clock showed it on that day: the calculator takes care of converting it to universal time, daylight saving time included. If your municipality is not in the list, choose «Other place in Italy» and enter latitude and longitude in decimal degrees, even with a comma as decimal separator (for example 41,9 and 12,5). The cities in the list use coordinates approximated to the town centre: for a municipality far from the provincial capital it is better to enter its own.
Calculation example
A person was born in Milan on 20 August 1975 at 14:00. Daylight saving time was in force that day, from 1 June to 28 September, so 14:00 Italian time corresponds to 12:00 UTC. The calculator returns the summary «Sun in Leo, Moon in Aquarius, Ascendant Scorpio» and these positions:
| Point | Position | House |
|---|---|---|
| Sun | 26°51′ Leo | 9 |
| Moon | 12°08′ Aquarius | 3 |
| Mercury | 14°23′ Virgo | 10 |
| Venus | 7°47′ Virgo R | 10 |
| Mars | 3°26′ Gemini | 7 |
| Jupiter | 24°39′ Aries R | 5 |
| Saturn | 27°01′ Cancer | 8 |
| Uranus | 29°11′ Libra | 11 |
| Neptune | 9°01′ Sagittarius R | 1 |
| Pluto | 7°33′ Libra | 11 |
| Ascendant | 20°39′ Scorpio | 1 |
| Midheaven | 5°35′ Virgo | 10 |
Venus, Jupiter and Neptune are retrograde. With the orbs used, the calculator finds fifteen aspects, including the Sun–Jupiter trine and the Venus–Neptune square, which is the tightest (1.2°).
Limits of the calculation
- It is designed for births in Italy: it uses the Italian time zone and accepts coordinates between 35° and 48° north and between 6° and 19° east.
- For 1943-1945, when time rules could differ between German-occupied territory and liberated territory, the calculator uses those of Rome.
- On the nights when the clocks change, one hour is repeated or does not exist (since 1980, the one between 2 and 3): for the repeated hour the calculator uses standard time.
- For future dates the Moon is slightly less accurate, because the Earth’s future rotation is not known exactly.
Frequently asked questions
What do I need to calculate my birth chart?
You need your date, time and place of birth; the time must be entered as Italian time of that period. If you don’t know it, it is stated in your birth certificate, as required by article 29 of DPR 396/2000 (Presidential Decree on the civil registry system): you can ask for it at the civil registry office of the Comune (municipality) where the birth was registered.
Can I calculate my birth chart without the time of birth?
Yes, by ticking «I don’t know the time»: the calculator uses noon and shows the planets in the signs and the aspects, excluding those of the Moon, but not the Ascendant, Midheaven and houses, which depend on the time. The Moon moves 12-15 degrees per day, so its position may be off by up to about 8 degrees and, near the border between two signs, even the Moon sign may change.
Does the calculator take daylight saving time into account?
Yes. In Italy daylight saving time was applied from 1916 to 1920, from 1940 to 1948 and then every year since 1966. The calculator converts the time using the browser’s international time zone database (IANA), which for Italy follows the dates published by INRiM, the Istituto nazionale di ricerca metrologica (Italian National Institute of Metrological Research). The exception is the period between 1943 and 1945, when rules could differ between German-occupied territory and liberated territory: for those births, check the time carefully.
Does the birth chart have a scientific basis?
The positions do: they are the real astronomical positions of the Sun, Moon and planets, compared with NASA’s JPL Horizons ephemerides. The meaning of signs, houses and aspects, however, belongs to the astrological tradition, which is not a scientific discipline: the birth chart is a curiosity, not a tool for making decisions or predictions.
Related tools: the Ascendant calculator, if that is all you need, and the guide to calculating the Ascendant.
