Rectangle area calculator
Calculate rectangle area in square meters or square feet from length and width. Useful for flooring estimates, room planning and material orders.
Last updated: May 2026
Enter length and width to calculate the area.
Rectangle area: flooring, tiling and room planning
Area = length — width. The result in m² tells you how much material you need to cover a surface. For flooring and tiling, always add 10–15% for cutting waste and breakage — diagonal tile layouts can require up to 20% extra. For paint, a rule of thumb is 10–12 m² per litre for a single coat on smooth plaster.
Non-rectangular rooms can be split into rectangles: calculate each section and add the results. An L-shaped room is two rectangles; a room with a bay window is the main rectangle plus the bay. The calculator handles one rectangle at a time.
Common room and surface dimensions
| Room type | Typical dimensions (m) | Area (m²) |
|---|---|---|
| Small bedroom | 3 x 3.5 m | 10.5 m² |
| Double bedroom | 3.5 x 4 m | 14 m² |
| Living room | 4 x 5 m | 20 m² |
| Large living room | 5 x 6 m | 30 m² |
| Garage (single) | 3 x 6 m | 18 m² |
| Tennis court | 10.97 x 23.77 m | 261 m² |
Frequently Asked Questions
How do I use this for non-rectangular rooms?
Split the floor plan into rectangles, calculate each area separately, then add them together. An L-shaped room = two rectangles. A room with a chimney breast = total rectangle minus the chimney protrusion (a small rectangle to subtract). For irregular shapes, break into as many rectangles as needed.
Why does my flooring estimate come out wrong?
Two common reasons: forgetting the waste allowance (10–15% for straight lay, up to 20% for diagonal patterns), and using internal wall measurements instead of the full floor area. Skirting boards and fitted furniture do not reduce the amount of flooring you need to buy — boards are cut to size on site.
What is the difference between area and perimeter?
Area (m²) measures the surface inside the rectangle — used for flooring, tiles, paint, carpet. Perimeter (m) measures the total edge length — used for fencing, skirting board, wallpaper border. Perimeter = 2 — (length + width). Neither can substitute for the other in a materials estimate.