How to calculate the square area

How to calculate the area of a square or circle for quantities or when pricing. Use for walls, floors, roofs etc.

You will often be required to calculate the square area of a floor, wall or similar especially when estimating and pricing up Carpentry work.

To calculate the area of a room like in the picture below whether its in centimetres, metres, feet or any other measure all you need to do is measure the length of the room, and the width. Then, simply multiply the length (side A) by the width (side B).

A x B = area2
how to calculate square area

If you are calculating the area of a floor to know how much laminate flooring to allow for I normally add between 5-10% extra to allow for cutting waste. To do this, multiply the answer by 1.05 or 1.1,

Answer x 1.05 = 5% extra added for waste.

Answer x 1.10 = 10% extra added for waste

How to calculate the area of an L shaped room

If the room/wall/shape you want to work out the area for isn't square but odd or L shaped like in the picture below, I separate the room into two or more manageable sections. Imagine a line separating the two sections like the red one in the picture.

how to calculate L shaped square area

Then, treat these as two separate rooms and calculate them as in the first example. After that, simply add the two answers together.

A x B = area2 1

C x D = area2 2

area 1 + area 2 = total area2

Circle square area and maths

Quite often as a carpenter I have needed the circle formulas information on this page to help calculate the amount of materials I need for floors for example and when forming arches for bricklayers.

If you are calculating the area of a round room in order to calculate how much flooring you will need, always allow a decent amount extra because there will unfortunately be more wastage than in a square room.

circle maths

Radius = The distance from the outer edge to the centre.

Diameter= The furthest distance possible across the width (twice the length of the radius).

Circumference = Distance all the way round the outer edge. (I've only ever used that once to work out the length of skirting needed for a round room).

When making some of the calculations a number called Pi is often needed. Pi is a decimal value, that we will simplify to 3.14 for the purpose of these calculations.

These are some of the things you can calculate using Pi and the radius of a circle;

  • Area = Pi r2 (Pi x (rxr))

  • Circumference = Pi x Diameter

  • Volume of a cylinder = Area x height or (Pi r2) x H
  • Have a question or comment about calulating the square area?