Home & workshop Areas

Room area calculator

Measure in

Length

Width

Ceiling height

Doors and windows

m²

Total area to deduct from walls

Floor area 14.4 m²

4.5 × 3.2 × 2.4 high

Everything else the measurement gives you

Floor area 155 ft²

Wall area (net) 33.76 m²

Perimeter 15.4 m

Volume 34.56 m³

Square yards 17.22 yd²

Floor, walls, perimeter and volume from one measure

Floor area is length times width. Wall area is the perimeter times the ceiling height, minus doors and windows. Volume is floor area times height. A 4.5 × 3.2 m room with 2.4 m ceilings has 14.4 m² of floor, 33.7 m² of wall after openings, and 34.6 m³ of air.

How to measure a room

1 Measure length and width at floor level, at the widest points.

2 Measure ceiling height from finished floor to ceiling.

3 Estimate the door and window area to deduct — a standard door is about 1.8 m².

4 Read floor, wall and volume figures together.

The volume figure is the one people skip and then need. It sizes heating and cooling, it sets ventilation requirements, and it is what a dehumidifier or air conditioner is rated against. The perimeter matters too: it is the length of skirting, coving or beading you will buy, and it is the number for a wallpaper order. Measuring once and reading all four figures is the entire point of doing it in one place rather than four.

Questions

How do I calculate room area? −

Length times width, both in the same unit. For an irregular room, split it into rectangles and add them.

What should I deduct for a door? +

Why does room volume matter? +

Should I measure at floor or waist height? +

Is floor area the same as usable area? +

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