Learn how to calculate the areas of rectangle, triangle, and circle in Excel for a single cell or range of cells usin this formula.

The area of a circle is pi times the radius squared. This is half of a circle with a radius of 1 (no units) such that it would have an area of pi/2.

Hmmm. . .the easiest way I can think of is to turn the circle into a polygon, clip using the rectangle, and then calculate the remaining area. This gives you an arbitrarily precise answer, though ...

Calculating the area of a circle To illustrate the formula for the area of a circle: A circle can be cut into sectors ... . The sectors can be rearranged to form an approximate ... rectangle shape.