Room Area Calculator

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.

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Also see
Length A*, mm
Length B*, mm
Length C*, mm
Length D*, mm





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
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