The **gon** is a measurement of plane angles, corresponding to 1/400 of a full circle, thus dividing a right angle in 100. The unit is also known as the **grad** or **grade**. One gon is equal to 9/10 of a degree or π/200 of a radian.

The unit originated in France as the **grade**, as part of the all metric system. Due to confusion with existing *grad(e)* units of northern Europe, the name *gon* was adopted. In Germany, the unit is also known as the *Neugrad* (new degree).

Although attempts at a general introduction was made, the unit was really only adopted in some countries and for specialized areas, like land measurement. The familiar degree (1/360 circle) or the mathematically convenient SI unit of angle, the radian (1/2π of a circle), are generally used instead of the gon.