**Circular orbit speed calculator by orbsi.uk**

Calculates the circular orbit speed of a planet of negligible mass orbiting a single star.

This calculator is for any system of units in which the gravitational constant **G = 1**.

Such units are often used in orbit simulation software. The equation is simply

An example of a useful and natural system of units in which G = 1, is defined like this:

Unit of mass = the mass of our Sun.

Unit of distance = 1 AU = the distance of our Earth from our Sun.

Unit of time = 1 Earth year divided by (2 * pi).

Unit of velocity or speed = the average orbit speed of our Earth.