Room Area Calculator
Calculate floor area, ceiling area and net wall area before choosing flooring or paint quantities.
How to use this calculator
- Measure the relevant dimensions and select each input’s unit. Changing units converts your entered value.
- Use the coverage, dimensions or yield for the actual product you plan to buy. The starting numbers are worked examples.
- Calculate, review the assumptions below and check the final order against the project and supplier information.
Formula
Floor/ceiling area = length × width. Perimeter = 2 × (length + width). Net walls = perimeter × height − openings area.
Worked example
A 5 m × 4 m room has 20 m² floor area and an 18 m perimeter. At 2.4 m high, subtracting 4 m² openings leaves 39.2 m² of walls.
Common mistakes and limitations
Rectangular room and equal wall heights only. Opening area is subtracted from walls, not from the floor or ceiling. No alcoves, sloped ceilings, skirting deduction, product allowance or layout optimization.
Questions about room area
Are walls and ceiling combined?
No. The result shows them separately so you can price different products or coats without double counting.
How should I measure an irregular room?
Split it into non-overlapping rectangular parts and calculate each. Check shared boundaries before adding wall areas.