Orbital Period Calculator

Calculate orbital period using Kepler's laws. Find orbital velocity, angular velocity, and perihelion/aphelion distances.

Semi-Major Axis

Central Mass

Solar Masses

Orbital Eccentricity

Tab to move between fields

Orbital Period

1 years

Orbital Period

365.25 days

Orbital Velocity

29,785.68 m/s

Angular Velocity0.017202 rad/day

Perihelion Distance1 AU

Aphelion Distance1 AU

How to Use This Calculator

Enter the Semi-Major Axis (AU) of the orbit — Earth's is 1 AU, Mars is 1.524 AU.
Enter the Central Mass (solar masses) of the star or body being orbited — the Sun is 1 M☉.
Set Orbital Eccentricity (0–0.99): 0 is circular, Earth's is 0.017, Pluto's is 0.25.
Read Orbital Period (years and days), Mean Orbital Velocity (m/s), and Perihelion/Aphelion distances (AU).
Use the orbital period to plan observation timing or to verify radial velocity measurements.

How the result changes with Semi-Major Axis

Semi-Major Axis	Orbital Period	Orbital Period	Orbital Velocity
10	31.623 years	11,550.22 days	9,419.06 m/s
35	207.063 years	75,629.68 days	5,034.7 m/s
65	524.047 years	191,408.08 days	3,694.46 m/s
90	853.815 years	311,855.92 days	3,139.69 m/s

Semi-Major Axis: Average distance from central body (1 AU = Earth-Sun distance)
Central Mass: Mass of central body in solar masses
Orbital Eccentricity: Orbit eccentricity (0 = circular, <1 = elliptical)

T² = (4π² / GM) × a³ (Kepler's Third Law)

Identify Input Parameters
Semi-Major Axis = 1, Central Mass = 1, Orbital Eccentricity = 0 = 3 input(s) provided
Calculate Orbital Period
Orbital Period
1 = 1
Calculate Orbital Period
Orbital Period
365.25 = 365.25
Calculate Orbital Velocity
Orbital Velocity
29785.68 = 29785.68
Calculate Angular Velocity
Angular Velocity
0.017202 = 0.017202
Calculate Perihelion Distance
Perihelion Distance
1 = 1