The blade diameter is critical because one, it determines the depth of cut, and two, the speed of the saw, which is expressed in rotation per minute (rpm).
The blade diameter would depend on the saw with which it will be paired with. Most circular saws can accommodate a 7 and 1/8-inch diameter blade. This can give a cutting depth of 2.25 inches. Table and miter saws, on the other hand, require blades with 10 to 12-inch diameter.