Work out planet orbital period (kepler) instantly with clear inputs, formula shown and shareable results.
Kepler's third law in solar units is beautifully simple: the period in years is the square root of the semi-major axis in AU cubed, divided by the central mass in solar masses. Mars at 1.524 AU gives 1.881 years, or 687 days, with a mean orbital speed of 24.1 km/s. Period squared equals axis cubed exactly for a one solar mass primary.
Kepler's third law
T^2 = a^3 / M, with T in years, a in AU and M in solar masses
Circular orbital velocity
v = sqrt(GM / a)
Because Earth's orbit is defined as 1 AU and 1 year around 1 solar mass, so all the constants become one.
Only slightly. Strictly the sum of both masses appears, but for planets around stars the planet's contribution is negligible.