Room Area Calculator

Our calculator can help you find the square footage of a rectangular or square shaped room. Learn how to calculate room area using the formulas.

All calculators
Also see
Application starting
Choose saving method
Download PDF
Download calculate with your chosen settings in PDF format — drawings + data.
Share in social network
Share the link to the calculation on Facebook, Twitter, Google+, etc.
Embed a calculator on your website for FREE

How to calculate room area?

A room is a living space bounded on all sides by walls and equipped with a separate passageway. We suggest using the free tool from KALK.PRO, it will help you quickly estimate the total area of the room, by length and width of the floor/walls. The tool can only be used for square and rectangular shaped rooms, if you have a non-standard room, scroll just below. To start the calculation, enter the length of each wall of the room: A, B, C, D and click "Calculate" to get the result.


Area of a room with four walls


Room area calculation formulas

The area of a quadrilateral room in our online calculator is calculated using the Brahmagupta formula:

  • Sroom = ((p − a) × (p − b) × (p − c) × (p − d))1/2, where a, b, c, d – sides of a quadrangle, p – half-perimeter of a quadrilateral (which is based on the formula: p = (a + b + c + d) / 2).

If you want to calculate the area of a room with five, six or more walls - the easiest way is to divide the room surface into simple shapes (square, rectangle, triangle, trapezium), use standard mathematical formulas and add up the values.

  • Triangular room area formula: S = (a × h) / 2, where а – base, h – height.
  • Square room area formula: S = a2, where а – side.
  • Rectangular room area formula: S = a × b, where а, b – sides.
  • Trapezoid room area formula: S = ((a + b) × h) / 2, where a, b – bases, h – height.
Non-standard shaped room area
Rate this page:
(estimate: 5, votes: 239)