Measure room and wall area before buying materials
Start with the surface you will actually cover. This guide helps you divide an awkward room, subtract openings and reuse the measurements without confusing installed area with the quantity you need to buy.
Back to calculator ↑Measure and divide the space
Sketch the outline and divide it into rectangles that do not overlap. Measure each section in metres. An L-shaped floor can usually become two rectangles meeting at one edge. Enter the width and length of each and choose Add area.
For a wall, use width and height instead. Measure unpainted doors or windows separately and choose Subtract area. Keep wall and floor calculations separate if they will use different materials. A tape or laser measure gives dimensions; the calculator cannot check whether your sketch overlaps.
Worked example: two sections and an exclusion
The first section is 4 m × 5 m, giving 20 m². An adjoining section is 2 m × 1.5 m, giving 3 m². An uncovered 1 m × 1 m opening removes 1 m². The net result is 20 + 3 − 1 = 22 m².
Enter two Add sections and one Subtract section. The breakdown should show 23 m² added and 1 m² deducted. The resulting 22 m² is the net surface, before any cutting allowance or package rounding. This makes the figure reusable even if you change the material later.
Carry the area into a material calculation
The result links carry net area into paint, tiles, SPC, vinyl or laminate. The destination still needs product details: paint coats and coverage, or flooring coverage per box and cutting allowance. Check those against the exact product you intend to buy.
Do not subtract the same doors again after sending net wall area to paint. The tile transfer sets its separate deduction to zero because exclusions have already been removed. Check the floor or wall selection before shopping. A large purchase quantity does not change the measured area used for labour or other installed-area costs.
Check the measurements before ordering
Convert centimetres before entering them: 80 cm is 0.8 m. Do not enter 80 for a small opening or subtract the same opening from two sections. The net total must remain positive. Recheck unusually large results against your sketch.
This tool supports up to 12 rectangular sections. It does not calculate perimeter or produce a cutting layout. Curved boundaries, sloping walls and diagonal edges need appropriate additional geometry. Treat a rectangular approximation as an estimate and confirm the surface before placing a material order.
Common questions
Can I calculate all four walls?
Yes. Add each wall using width × height, then subtract doors and windows that will not be painted.
Does the result include waste?
No. Choose cutting or application allowance in the destination material calculator so it is applied only once.
How are square metres different from metres?
Metres measure length; square metres measure surface area. A width of 4 m multiplied by a length of 5 m gives 20 m², not 20 metres.
Sources and calculation guidance
Check these against your chosen product’s label and instructions.