Planning
Turn two measurements into a usable surface area. This calculator suits a rectangular floor, wall, ceiling or sheet, with an optional deduction for openings. Use the net result as the starting quantity for flooring, paint, glass or other materials sold by area.
Your estimate
Net area = length × width − excluded area.
For an irregular shape, split it into rectangles and add their areas. This calculator handles one rectangle at a time.
Currency labels do not convert prices. Enter all prices in the chosen currency.
Enter the length and width of one rectangle in the units shown. Subtract the combined area of openings or excluded sections. For an irregular space, calculate separate rectangles and add their net areas.
A 5 m by 4 m room has an area of 20 m². Subtracting an excluded area of 1.5 m² leaves 18.5 m². Material waste is added separately when estimating what to buy.
Gross area = length × width. Net area = gross area − excluded area. For a wall, enter its height as one of the two dimensions. The excluded area is the combined area of the parts you do not intend to cover, entered in the square unit shown beside the field.
Measure each opening separately before adding the deductions. A 0.9 m × 2.1 m doorway occupies 1.89 m². Do not enter 0.9 as the deduction: that is a length, not an area. Deductions cannot exceed the gross surface.
A square metre and a square foot describe area, not length. One square foot equals 0.09290304 m². Convert both dimensions before multiplying, or convert the completed area using the area factor. Multiplying an area by the ordinary feet-to-metres factor gives the wrong result.
For decimal feet, 10 ft 6 in is 10.5 ft because 6 ÷ 12 = 0.5. It is not 10.6 ft. Keep measurements in the selected unit, and check the unit labels whenever you switch systems.
Divide an L-shaped room into non-overlapping rectangles. Calculate each rectangle and add their areas, making sure a shared section is counted only once. A bounding rectangle can also work if you deduct the missing rectangle. Curves and sloping surfaces need their own geometry or measured surface area.
The result is measured coverage. Material waste, overlaps, pack rounding and cutting layouts belong in the next estimating step. Keeping those separate makes it easier to compare products without changing the room measurement.
Worked example
A room measuring 5 m × 4 m has a gross area of 20 m². An excluded 1 m × 1.5 m section removes 1.5 m², leaving 18.5 m². At 10% material allowance, a separate ordering calculation would use 20.35 m².
Calculate each room separately and add the net areas. Keep a labelled measurement list so you can check which closets, alcoves and connecting spaces are included.
No. This tool calculates area only. Use the tile, flooring or material calculator for the next quantity or pricing step.
Manufacturer and measurement references for the assumptions described above.