How do I calculate the area of an L shaped room?

Split it into two rectangles, work out each one and add them together. Any awkward shape can be handled the same way.

How do I work out the area of a circle?

Pi times the radius squared. Measure across the widest point to get the diameter, halve it for the radius, then square it and multiply by pi.

How do I calculate a triangle area?

Base times height divided by two. The height is measured straight up from the base, not along a sloping edge.

What about a curved wall?

Split the curve into a series of short straight segments and treat each as a rectangle. For ordering material that is accurate enough.

Do I add or subtract for a cut corner?

Work out the whole rectangle and subtract the triangle that has been taken off. That is usually easier than adding several pieces.

Should I measure in metres or feet?

Whichever you prefer, as long as everything on the job uses the same one. Mixing units halfway through is the most common source of error.

Area Calculator

Shape

First dimension

Length, diameter, or base.

Second dimension

Width or height. Not used for a circle.

Third dimension

For an L shape, the length of the second leg.

Fourth dimension

For an L shape, the width of the second leg.

How many of this shape

Your answer

Area

20 m2

That is 215.3 square feet.

Shape: Rectangle
One of them: 20 m2
How many: 1
In square feet: 215.3 sq ft
With 10 per cent wastage: 22 m2

For a circle, put the diameter in the first box. The tool halves it to get the radius.

Area Calculator for Dubai and the UAE

This tool works out area for shapes that are not simple rectangles. Circles, triangles and L shaped rooms all come up in real buildings.

Pick the shape, put the dimensions in, and it gives you the area in square metres and square feet.

For a plain rectangular room the room area calculator is quicker. This one is for everything else.

The four formulas

Simple enough to check by hand, which is worth doing at least once.

Rectangle
Length times width. The one everybody knows and the one most rooms are.
Circle
Pi times the radius squared. The radius is half the diameter, so measure across the widest point and halve it.
Triangle
Base times height divided by two. The height is measured straight up from the base, not along a sloping side.
L shape
Split it into two rectangles, work out each, and add them. This is how every awkward room is handled.

Where these shapes appear in real buildings

More often than you would expect once you start looking.

L shaped living rooms
Very common in apartments here, especially where a dining area comes off the main space.
Circular features
A round rug area, a curved feature wall, a circular ceiling detail or a round table space in a majlis.
Triangles under sloped ceilings
Where a wall meets a sloping roof, the top of that wall is a triangle. Common in villa top floors.
Angled corners
A room with a cut corner is a rectangle with a triangle taken off it.
Pool surrounds
Rarely a plain rectangle. Usually a shape that has to be split into parts.
Terraces and balconies
Often tapered or angled to fit a building envelope.

Splitting a complicated shape

Almost any floor plan can be handled by splitting it into rectangles and triangles. There is no shape too complicated for this method.

Draw the outline roughly on paper. Then draw straight lines across it to cut it into pieces you can measure.

Work out each piece and add the totals. Do them one at a time and write each result down rather than trying to hold them in your head.

For a shape with a bite taken out of it, work out the whole rectangle and then subtract the missing piece. That is often easier than adding several parts.

For curves, split the curve into a series of straight segments. It is not exact, but for ordering material it is close enough and it is far easier than trying to be precise.

The only rule is to be consistent about units. Everything in metres, or everything in feet, and never a mix.

What to do with the answer

Area is the starting point for almost every material you buy for a building.

For flooring, add wastage and order. For paint, multiply by coats and divide by coverage. For tiles, divide by the tile size.

For a quote, area times a rate per square metre is how the price is built.

What area cannot tell you is anything about the perimeter. Skirting, cornice and trim are bought by the metre around the edge, which is a different measurement entirely.

And for anything where the price per square metre is high, measure twice. On marble or stone, a small error in area is a real amount of money.

Questions people ask

How do I calculate the area of an L shaped room?: Split it into two rectangles, work out each one and add them together. Any awkward shape can be handled the same way.
How do I work out the area of a circle?: Pi times the radius squared. Measure across the widest point to get the diameter, halve it for the radius, then square it and multiply by pi.
How do I calculate a triangle area?: Base times height divided by two. The height is measured straight up from the base, not along a sloping edge.
What about a curved wall?: Split the curve into a series of short straight segments and treat each as a rectangle. For ordering material that is accurate enough.
Do I add or subtract for a cut corner?: Work out the whole rectangle and subtract the triangle that has been taken off. That is usually easier than adding several pieces.
Should I measure in metres or feet?: Whichever you prefer, as long as everything on the job uses the same one. Mixing units halfway through is the most common source of error.

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