Square Footage Calculator

Not Reviewed
Calculator / Last modified by pro on 2017/04/25 17:24
Area of Rectangle
Area of Quadrilateral
Area of a Triangle (base and height)
Area of a Triangle (three sides)
Area of Polygon
Area of Circle = `pi*r^2`
Ellipse Area

The Square Footage Calculator helps you compute the square footage of an area like room (e.g. kitchen or living room) based on some simple measurements and the shape of the area.square footage.png

INSTRUCTIONS::  To compute the square footage of the area, you must first identify the shape of the area.  The common choices are:

  • Four Sided Areas:  Most rooms are simple rectangles.
    • Rectangle
    • Quadrilateral
  • Circular Areas
    • Complete Circles
    • Ellipse
  • Three Sided (Triangles)
    • If you know the base (b) and height (h)
    • If you know the length of three sides (a, b, c)
  • Many Sides
    • Polygons

A Word on Units

The measurements you will enter into the calculators are all lengths and a few angles.    The measurements can be in any of a large number of different types of length units.  These units go from very small nano-meters to huge astronomical units like light years.  The formulas all work with all the different units, but unless you're a rocket scientist or a micro-biologist, you're probably computing the square footage of an area measured in feet or maybe inches.  Beside each input field, you will see a symbol that indicates the default units (e.g. ft for feet).  If you click on that symbol, you can choose different units that are comfortable for you. 

How Area is Used

The calculator helps you compute the square footage of an area, but when will I need it?  One big use of square footage is when you are thinking about buying or selling a house.  Square footage is one of the basic metrics used in any listing.  Click HERE for a good article on the subject by Margaret Heidenry at Realtor.com.  Many jobs, especially Do-It-Yourself jobs, require that you know the square footage of an area before you can intelligently buy supplies.  This is common inside the house and office and outside in landscaping.  Here are few related calculators that are use square footage in calculating materials needed for jobs.

The Math

We run into different geometric shapes in buildings.  Here are the most common.

  • Four Sides -  This is can be a simple square with four right angled sides, a rectangle with right angled corners and a different length and width, a simple quadrilateral with four different but straight sides, a trapezoid with four sides where two sides are parallel, and a parallelogram where there four sides where the opposite sides are parallel.
  • Circular - Hopefully we all know what a circle looks like.
  • Elliptical - This is a flattened circle or oval (see diagram).
  • Three Side - This is a triangle
  • Many Sides - This is a polygon.  The formulas work for any number of equal sided shapes with equal angles.