In the same way that we should always use rulers when we draw shapes like triangles and squares, whenever we draw circles we should always use a compass. A compass is a specialized tool that allows us to draw circles of a specific radius.
There are two main types of compasses: compasses with pencil holders, and compasses with a built in pencil.
Set your compass width by either moving the compass arms or twisting the dial, depending on the type of compass you have. This width will be your circle's radius.
Place the needle where you want the centre of the circle to be.
Without changing the compass width or moving the needle, rotate the other arm around the centre to draw the circle.