Planets - Calculate Circumference

Calculator for the equatorial circumferences of Sun, Moon, Earth and the planets in kilometers, miles and compared to each other. Large celestial bodies are not spheres, but are oblate at their poles. Therefore, their circumference is the largest at the equator. This circumference is the longest closed path that can be traveled before returning to the starting point. The equator is the only great circle of a non-spherical planet or star.

Kilometers:
Miles:
Circumference		km mile Earth circ. Jupiter circ. Sun circ.
Moon:
Mercury:
Venus:
Earth:
Mars:
Jupiter:
Saturn:
Uranus:
Neptune:
Pluto:
Sun:

Round to   0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15   decimal places.

Please enter one value, the other values will be calculated.

Example: Jupiter has about eleven times the circumference of Earth. This, with its fourty thousand kilometers, has almost four times the circumference of the Moon.

Circumference or perimeter is a one-dimensional quantity, like the radius, even though it extends across two dimensions. Consequently, circumference increases linearly with the radius, unlike, for instance, surface area. Thus, for a given shape, doubling the radius results in doubling the circumference.

There is a well-known numerical trick that seems surprising at first glance but makes perfect sense upon closer inspection. If you wrap a rope around a ball, make the rope one meter longer than the distance required to encircle the ball, and then position it at a uniform distance from the ball's surface, that distance will be slightly less than 16 centimeters (specifically, 100 cm / 2π). If you were to wrap the rope around the Earth and make it one meter longer than necessary, the gap between the Earth's surface and the rope would be exactly the same size. This principle applies to any object with a circular perimeter, including other planets. The circumference of a circle with radius r is calculated as 2 π r. If the round object has radius r, the rope, lengthened by l, is at a distance s from the object, and c is the object's circumference, then c = 2 π r and
c + l = 2 π ( r + s ) = 2 π r + 2 π s = c + 2 π s
It follows that l = 2 π s. The original radius r no longer appears in this equation.

Last updated on 07/31/2026. Author: Jürgen Kummer

Calculators for Planets and Astronomy

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