From Armchair Design:
Designing a new home? Working on a remodeling project or space planning? Home Sizer is the perfect tool for anyone wanting to estimate the size and function of their dream home, or to just calculate the square footage of an existing home.
Home Sizer allows you to enter the dimensions and name of each room while it calculates the area of the rooms as well as the cumulative usable square footage and estimate gross square footage of the entire house.