Type the date, the time and the place above and press the button. The calculator turns them into a moment in universal time and a point on the globe, works out where each body stood at that moment, and draws the chart. What makes the result different from most calculators is that you can check it: the same numbers for a fixed test birth are published next to NASA’s. They come from the Swiss Ephemeris, and the verification page shows how to repeat the check in five minutes.
What the calculation returns
- The chart wheel with all twelve houses.
- For each of the 17 bodies and points: its ecliptic longitude, its sign and degree, its daily motion, whether it is retrograde, and the house it falls in.
- The Ascendant, the Midheaven and the twelve Placidus cusps.
- The five major aspects between the bodies, each with its orb in degrees and whether it is applying or separating. Natal orbs are fixed: conjunction 8°, sextile 6°, square 8°, trine 8°, opposition 8°.
- The balance of elements and modalities, the Part of Fortune and the fixed stars close to a body.
Why the orb is named: a square 0°30′ from exact and a square 7°30′ from exact are both called a square, and they are not the same thing. The closer one is far stronger, so each aspect here comes with its orb in degrees. How orbs work
The same output on the published test chart
| Body | Position | House | Motion |
|---|---|---|---|
| Sun | 13°33′ Virgo | 7 | direct, 0.97°/day |
| Moon | 19°01′ Leo | 7 | direct, 14.60°/day |
| Mercury | 25°36′ Leo | 7 | direct, 0.84°/day |
| Venus | 21°54′ Leo | 7 | retrograde, 0.27°/day |
| Mars | 3°28′ Libra | 7 | direct, 0.65°/day |
| Aspect | With | Orb |
|---|---|---|
| Trine | Neptune | 0.55° |
| Trine | Juno | 2.28° |
| Sextile | Ceres | 2.48° |
| Trine | Uranus | 3.64° |
Demonstration birth: 1991-09-06 at 18:30 local time, Kyiv, Ukraine (50.4501° N, 30.5234° E), Europe/Kyiv at UTC+3, so 1991-09-06 15:30 UTC. Tropical zodiac, Placidus houses, Swiss Ephemeris 2.10.03. Download the full result (JSON) or see how to verify it.
Tropical zodiac, Placidus houses
Every chart here is tropical and Placidus. The tropical zodiac starts at the March equinox, which is the convention of western astrology; the difference from a sidereal zodiac is explained in tropical vs sidereal. Placidus divides the sky by the time a degree takes to travel between the horizon and the meridian; how it differs from Whole Sign is in Placidus vs Whole Sign. There is no setting to change either one, and the node is the true node.
If you do not know the birth time
The planets barely notice the hour: over a day the Sun moves about one degree and the slow planets far less, so their signs are calculated as usual. The Moon moves twelve to fifteen degrees in a day, so it comes with a note. The Ascendant, the Midheaven and the houses depend on the minute, and without one they are undetermined. The calculator leaves them empty instead of showing a noon chart as if it were yours. Ways to recover the time are in how to find your birth time.
Your first reading in five minutes
- Planets. Ten of the seventeen bodies are the classical planets and the two lights. Each is a function: the Sun is direction, the Moon is need, Mercury is thinking, and so on.
- Signs. The sign is how that function behaves. Read the sign and the degree, not the sign alone: 2° and 28° of the same sign sit next to different neighbours.
- Houses. The house is where in life it happens. Houses depend on the birth time; without one they are undetermined, not approximate.
- Aspects. The angles between bodies, each with its orb. Start with the two or three tightest: they describe the chart better than a long list of wide ones.
The full walk-through, with a worked example on the published test chart, is in Reading your natal chart.
Thirteen calculators for one question each
If you came for a single answer, these pages calculate just that and explain it. All of them use the same engine as the full chart.
- Rising sign
- Moon sign
- Big Three
- Venus sign
- Mars sign
- Mercury sign
- Chart ruler
- North Node
- Part of Fortune
- Fixed stars
- Elements and modalities
- Chiron
- Lilith
Check the numbers
This is checkable. We publish the intermediate values of a fixed test chart, planetary longitudes to four decimal places and all twelve house cusps, next to the same values from JPL Horizons, which NASA publishes and we do not control. Across 15 bodies the largest difference is 0.53 arcseconds, and the method takes five minutes to repeat with any tool, including ours. See how to verify a chart and the accuracy report.
Questions
Is the birth chart calculator free?
Yes. The full chart, all six sphere readings and the Moon phase cost nothing, and you can see the chart without creating an account. An account is needed to save it. Paid plans add compatibility, locations and the year ahead; the calculation itself is the same on every plan.
Which house system and zodiac does it use?
Placidus houses and the tropical zodiac, and nothing else. There is no switch for Whole Sign, Koch or a sidereal zodiac. If you need one of those, this is not the right calculator for that chart.
Where do the numbers come from?
From the Swiss Ephemeris, library version 2.10.03, run with its data files. We publish a fixed test chart with every intermediate value next to the same values from NASA JPL Horizons, so the arithmetic can be checked by anyone.
What if I do not know my birth time?
Tick the box and calculate anyway. The planets are calculated for the day; the Ascendant, the Midheaven and the twelve houses are left undetermined rather than guessed, and the Moon carries a note on how far it can be off.
Can I calculate a chart for someone else?
Yes. Enter their date, time and place the same way. It is their personal data, so ask first. To compare two charts, use compatibility, which works from both.
How accurate is it?
For modern dates the planetary longitudes agree with JPL Horizons to within a fraction of an arcsecond on our published test chart. The largest source of error in practice is not the ephemeris but the input: a birth time rounded to the hour moves the Ascendant by many degrees.
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