Work out the three placements most charts start with, computed from real astronomical positions rather than date ranges.
How the natal chart calculator works
Most free sun-sign tools just look your date up in a table of ranges, which fails for anyone born near a cusp because the Sun does not change sign at the same moment every year. This calculator computes the actual solar longitude from your birth moment instead.
The Moon is computed with a standard low-precision series accurate to roughly a fifth of a degree, and the ascendant from local sidereal time and latitude. The ascendant is the placement most sensitive to birth time — it moves a full degree every four minutes.
Using the calculator
- Enter your birth date and time as precisely as you can.
- Enter the UTC offset that applied at your birth place and date.
- Enter the latitude and longitude of your birth place.
The calculation
A worked example
Take the starting scenario, a longitude of -0.13. That gives a sun sign of ♊ Gemini 23° 59′. Underneath, Moon sign comes out at ♑ Capricorn 27° 56′ and Rising sign at ♎ Libra 11° 05′. Change any field and every figure updates as you type.