Area Calculator

Formulas for the four common shapes

For a triangle, "height" means the perpendicular distance from the base to the opposite point — not the length of a sloping side. For a trapezoid, sides A and B are the two parallel edges.

Measuring rooms that aren't rectangles

Very few real rooms are a clean rectangle. The reliable approach is to split the floor into shapes you can measure and add the results:

1. Sketch the room roughly to scale.
2. Divide it into rectangles — most L-shaped rooms are two.
3. Measure each section and calculate its area.
4. Add them together, then subtract anything you're not covering, like a kitchen island.

Adding a waste allowance

Ordering exactly the measured area almost always leaves you short. Standard allowances:

• Plain tile or laminate, square room — add 5%.
• Awkward layouts, angled cuts — add 10%.
• Diagonal or herringbone patterns — add 15%.
• Patterned material needing alignment — add 15–20%.

Buying slightly over also gives you matching spares from the same batch, which matters if a section is damaged later — dye lots vary between production runs.

Units

Areas grow with the square of the linear unit, which trips people up: a room measured in centimetres gives an area in square centimetres, and there are 10,000 of those in a square metre. The calculator shows metric and imperial equivalents side by side so it's harder to slip a factor.