Whether you're preparing to sell your home or redesign your garage, it is always helpful to know just how much space you actually have in there. Calculating the square footage of your garage is a simple task that will give you the information you need to optimally utilize your garage's space.
Things You'll Need
 Paper and pencil
 Tape measure or sonic measuring device
 Calculator

Draw a rough sketch of the shape of your garage floor from a topdown view.

Divide your drawing into as few rectangles as possible, so that the drawing is composed entirely of sidebyside rectangles. If there are any angled walls in your garage, divide them off into right triangles, and then divide the remaining space into rectangles.

Measure the length of each of the sides of each rectangle in your garage. Write the length of each side next to the corresponding side in your drawing. If there are any triangles in your drawing, then measure their sides as well. Make all measurements in feet.

Multiply the length of one side of a rectangle by one of its adjacent sides (not the side on the opposite side of the rectangle). Write the result in the middle of the rectangle. Repeat for each rectangle in your drawing. If you have any triangles, multiply the sides adjacent to the right angle (the sides that aren't one of your garage walls) by each other and then divide the result by two. Write that result inside the triangle.

Add up all of the numbers inside the rectangles and triangles. Now you have your garage's square footage.