If you come across a lot of arcs which you want to create circles from you can use the 'Arc to Circle' command. With this command you can select the arcs you wish to convert. The circles can be created on the current layer but if you want the can also be created on the layers the arcs are on. If two arcs share a centre point and radius and are drawn on the same layer the command will create just one circle to prevent duplicate circles. If you want the selected arcs can be erased from the drawing straight away.