Area Calculator
Quick answer
Area of a rectangle is length × width. A room 5.2 m by 3.8 m is 19.76 m², which is 212.7 square feet.
Room or plot area
Rectangular spaces. Split an L-shape into two and add the results.
5% straight lay · 10–15% diagonal or herringbone.
Area
19.76 m²
In square feet
212.7 ft²
Order with waste
20.75 m²
Perimeter, useful for skirting: 2 × (length + width).
Room area is the starting point for almost every material estimate in a house — flooring, tiles, paint, underlay, skirting. Getting it right once saves recalculating each time, because everything else is a rate applied to this one number.
The mistake that costs money is ordering exactly the calculated area. Cuts, pattern matching and breakage mean flooring and tiling always need a waste allowance, and the allowance is larger than most people assume.
Waste allowances that trades actually use
Straight-laid flooring in a simple rectangular room needs about 5 per cent extra. Diagonal laying, herringbone or a room with several alcoves pushes that to 10 or even 15 per cent, because every direction change creates an offcut too short to reuse.
Tiles follow the same logic with an added constraint: buy the whole quantity in one batch. Ceramic and porcelain shade varies between production runs, and a replacement box bought months later rarely matches under daylight.
Converting between metric and imperial
One square metre is 10.764 square feet. The conversion trips people up because the linear factor is 3.281 and the squared factor is its square, so a room that is 20 per cent longer in feet is 44 per cent larger in area.
For irregular rooms, split the floor into rectangles, calculate each separately and add them. It is faster and less error-prone than trying to find a single formula for an L-shaped space.
Frequently asked questions
- How do I calculate an L-shaped room?
- Divide it into two rectangles, calculate each area separately and add them together. Measure the shared edge once and be careful not to double-count it.
- How much extra flooring should I order?
- About 5 per cent for a straight lay in a simple room, 10 to 15 per cent for diagonal or herringbone patterns and rooms with alcoves or bay windows.
- How many square feet is a square metre?
- 10.764 square feet. To go the other way, multiply square feet by 0.0929.
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Updated 2026-09-20 · all calculators. Results are estimates for guidance, not professional advice.