The Natal Chart:
The wheel grounds the Sun, Moon, and eight planets within the tropical zodiac. Every house and angle is anchored strictly by the recorded civil time and coordinates of your birth.
A local astronomical calculator
Your Birth Chart, Beneath the Sky That Held You
Enter your birth date, time, and location. Our on-device astronomical calculator seamlessly resolves historical time zones to map your tropical natal chart and the physical sky exactly as it was the moment you were born.
- Completely free
- No account required
- 100% private—your birth data never leaves your device.
Begin with the record
Calculate your chart
Only your browser performs the calculation. Your birth inputs are not included in any network request.
The instrument at rest
Your wheel begins with the record
This uncalculated guide shows the twelve-sign structure only. It contains no planet, house, angle, or aspect claims. Enter the record above to replace it with your calculated chart.
Reading the Instrument
Decoding the heavens above:
The Physical Sky:
A mathematically true projection of the celestial dome. This model calculates equatorial positions, horizon geometry, proper motion, and atmospheric refraction to show the sky exactly as it was. (Note: Physical astronomical constellations differ from the stylistic divisions of the tropical zodiac.)
Time Uncertainty:
For vague or unrecorded times, the instrument samples the entire selected interval. We mark potential shifts in signs and aspects, deliberately withholding false precision so your data remains strictly factual.
Questions people ask
Is my birth data private?
Yes. Calculation, place lookup, timezone resolution, chart drawing, and exports run in the browser from same-origin files. Optional device storage is off until you select it.
Why does a repeated clock time need a choice?
When clocks move backward, one local time can name two different instants. The calculator presents both offsets and never chooses automatically.
What if I do not know my birth time?
You receive a date-only result sampled across the complete local civil day. Houses, angles, Rising sign, and birth-hour animal are withheld.
Are the zodiac and sky the same map?
No. The natal wheel uses twelve equal tropical zodiac signs. The sky dome uses physical horizon coordinates and official constellation line geometry.
What does estimated visibility mean?
It combines horizon position, catalog magnitude, and twilight. It cannot know the historical weather, haze, buildings, eyesight, or local light.
Why might Placidus be unavailable?
Placidus can be mathematically undefined at high latitudes. The calculator reports that state and lets you explicitly choose Whole Sign or Equal House.
How is the Chinese zodiac result calculated?
It uses the traditional lunar year beginning at Lunar New Year, not January 1. The local calendar supplies the animal, Heavenly Stem, Earthly Branch, element, polarity, and lunar date.
What is the Chinese birth-hour animal?
It is the animal associated with the two-hour branch containing the resolved local birth time. It is withheld when the time is unknown and is not presented as a complete BaZi reading.
What if an approximate time crosses a Chinese hour boundary?
The calculator samples the selected interval and shows both possible hour animals and pillars instead of choosing one.
Is the Celtic tree result ancient?
No. It is clearly labeled as a modern correspondence calendar, versioned so its date ranges remain stable.
Does this cost anything to run?
No. It uses permissively licensed local software and static data. There is no subscription, paid API, or per-chart service.
Data and calculation credits
Planet positions use Astronomy Engine; historical timezone rules use Moment Timezone and IANA data; the place directory is derived from GeoNames under CC BY 4.0; star data is credited to ESA/Gaia/DPAC; and constellation line geometry comes from D3-Celestial under BSD-3-Clause. All chart calculation uses local software and same-origin static data.