This content is licensed under Creative Commons Attribution/Share-Alike License 3.0 (Unported). That means you may freely redistribute or modify this content under the same license conditions and must attribute the original author by placing a hyperlink from your site to this work https://planetcalc.com/5732/. Also, please do not modify any references to the original work (if any) contained in this content.
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.