Birth chart calculator
Ten planets, twelve houses, the aspects between them and the wheel itself. Any date from 1900 to 2200, computed on Swiss Ephemeris, free and without an account.
Chart calculator
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What a birth chart actually is
Take the sky as it looked from one spot on Earth at one instant, flatten it onto a disc, and mark where each planet stood. That disc is the chart. Everything else in astrology is a way of reading it.
The disc is cut two ways at once. The signs divide it by the seasons, starting from the spring equinox, and they say how a planet behaves. The houses divide it by the horizon at the moment of birth, and they say where in a life that behaviour shows up. A Mars in Aries in the tenth house and a Mars in Aries in the fourth are the same appetite pointed at two different halves of a life.
The three things people look at first
The Sun is the sign everybody knows. It describes what a person is working towards and what they are recognised for, and it moves slowly enough that everyone born within a few weeks shares it. That is exactly why a Sun sign on its own tells you so little.
The Moon changes sign every two and a half days and describes the private half: what settles someone, what they reach for when tired, how they were looked after as a child. Two people with the same Sun and different Moons are not much alike.
The Ascendant changes sign every two hours, which is why it needs an exact time. It is the horizon at the moment of birth, and it describes the manner people meet you in before they know you.
How to read the tables the calculator gives you
The planet table has a degree column. A degree is a position inside a sign, from 0 to 30, and it matters because aspects are measured from it rather than from the sign. Two planets can sit in signs that "should" be in harmony and be nowhere near an aspect.
The R column marks a retrograde: a planet that appears, from Earth, to be moving backwards. Nothing is actually reversing. Astrologers read it as the planet working inwardly rather than outwardly.
The dignity column says whether a planet is in a sign it finds comfortable. Domicile is its own sign, exaltation is the guest room where it is treated well, detriment and fall are the two awkward positions. It is an old scheme and a useful one: it tells you which planets in a chart are working from strength.
Questions
What do I need to build a birth chart?+
A date, a place and, if you have it, a time. The date sets the planets, the place sets the horizon, and the time sets which house each planet falls in. Without the time you still get a real chart; you get it without houses.
Where do I find my birth time?+
In the UK it is on the full birth certificate for twins and multiple births, and often nowhere else — the short certificate does not carry it. Hospital records, a baby book or a parent's memory are the usual sources. Anything to the nearest fifteen minutes is workable.
Which house system does this use?+
Placidus, which is what most Western astrologers work with and what almost every book assumes. Other systems divide the same sky differently: the planets stay where they are and only the boundaries move.
Why does my Sun sign differ from the one in the newspaper?+
Because the Sun changes sign on a slightly different day each year, and a birthday on the boundary can fall either side depending on the year and the hour. A calculator works from the actual position rather than from a fixed calendar of dates, which is why it occasionally disagrees with the magazine.
What is an aspect, in one sentence?+
An angle between two planets that astrologers read as those two parts of a life having something to say to each other — a trine at 120 degrees easily, a square at 90 degrees with friction.
Can I share the chart I built?+
Yes. Every calculation gets a permanent address of its own, and the link shows the same chart to anyone who opens it. It carries the moment and the place, and nothing about you.
And what does it mean?
The calculator shows what sits where. A personal reading takes the same chart and explains how it plays out: character, relationships, money, direction, written as prose rather than as a table.
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