Virtual Graph Paper

Thank you for the consideration. For me, the use cases are:
Connecting items together end-to-end, i.e. Both definition points are on the outside (vs. centre) of the circle.
Diameter is an odd number of grid squares (i.e. the radius is not a whole number of grid squares)
Item in question has ...

Is there a way to create a circle by drawing "according to" its diameter (vs. from the centre out using its radius)? If not, could there be?