gradian

Non-SI unit

Name	Symbol	Quantity	SI units
gradian, gon	gon	plane angle	^π⁄₁₈₀ rad
The gradian, or gon, symbol gon, is a non-SI unit of plane angle. The gradian is not accepted for use with the SI. By definition, one gradian is equal to ¹⁄₄₀₀ of a turn, or ^π⁄₂₀₀ radians.
Definition
$1 \mspace{4mu} \text{gon} = \dfrac{\pi}{200} \mspace{6mu} \text{rad}$

The gradian is a centesimal unit of angular measurement, with one gradian being equal to ¹⁄₁₀₀ of a right angle.

The conversion between radians and gradians follows from the relation: 1 turn = 400 gon.

$400 \mspace{4mu} \text{gon} = 2 \pi \mspace{6mu} \text{rad}\\ \\ \\ 1 \mspace{4mu} \text{gon} \mspace{16mu} = \dfrac{\pi}{200} \mspace{6mu} \text{rad}$

A simple decimal relationship between angle of latitude and distance along the Earth’s surface was one of the objectives of the metric system when it was originally developed. By defining the metre as ¹⁄_{10 000 000} of the distance along a meridian from the North Pole to the Equator, navigational calculations were able to be greatly simplified, with one gradian of latitude corresponding to a distance along the Earth’s surface of approximately 100 kilometres.