This calculator calculates total square as sum of squares of entered rectangles.
For example, you need to know total square of your walls, minus square of door and window. In this case total square will be sum of squares of four wall rectangles minus door square and window square.
Thus, when you are adding rectangle in table, you can choose whether you want to add or subtract its square to total square.
Digits after the decimal point: 2
Added square, square meters
Subtracted square, square meters
Total square, square meters