Planets

The period of rotation T of a planet is given by:
T² = (4π² / GM) r³

where G = universal gravitational constant = 6.6743 x 10^-11 N m² kg^-2
M = mass of the Sun = 1.9889 x 10³⁰ kg
r = radius of the orbit of the planet

This is Kepler's 3rd Law of Planetary Motion: T² is proportional to r³

Planet	Distance from Sun r (km)	Period of Revolution T (years)
Mercury	57 900 000	86 days
Venus	108 200 000	225 days
Earth	149 600 000	1
Mars	227 392 000	1.88
Jupiter	778 300 000	11.9
Saturn	1 427 000 000	29.5
Uranus	2 870 000 000	84.0
Neptune	4 497 000 000	164