Free Self-Discovery Tool
Free decan calculator: find the decan of your Sun, Moon, and Rising sign, the planetary sub-ruler of each, and what your decanates reveal about your chart.
A decan is a 10-degree slice of a zodiac sign. Every sign has three, covering 0 to 10, 10 to 20, and 20 to 30 degrees, and each is sub-ruled by a planet drawn from another sign of the same element. That sub-ruler tints how the sign expresses, which is why a first-decan Leo can feel noticeably different from a third-decan Leo even though both are Leos.
Take the exact degree of a planet within its sign: 0 to 9 degrees is the first decan, 10 to 19 the second, and 20 to 29 the third. This calculator does it automatically for your Sun, Moon, and Rising sign and names the planetary sub-ruler for each once you enter your birth date, time, and place.
Your Sun and Moon decans barely move over a day, so they stay accurate even without an exact time. Your Rising decan shifts roughly every four minutes, so an accurate birth time is essential for that line. Without it, the tool still shows your Rising sign but marks the decan as approximate and asks for your time.