Measure a room, wall, deck, or lot. Get square feet, square yards, square meters, and acres — plus a waste allowance and material cost, so you know what to actually buy.
Measure straight across the widest point, through the centre.
Perpendicular height from the base to the opposite point — not the sloped edge.
Four identical bedrooms, six matching wall panels — set it once, multiply here.
10% covers off-cuts on a standard job. Use 15% for diagonal layouts or patterned material.
120 sq ft measured, plus 10% waste
Breakdown
Same area, other units
For a rectangle, area is length × width. For a circle, it is π × radius², where the radius is half the diameter you measure across the widest point. For a triangle, it is (base × height) ÷ 2, using the perpendicular height rather than the sloped edge.
That result is multiplied by the number of identical areas, then increased by the waste factor to give the quantity you should actually order. Waste is not optional padding — off-cuts, damaged pieces, and pattern alignment consume real material, and returning to the supplier mid-job for two more boxes from a different dye lot is how floors end up mismatched.
If you enter measurements in meters, every linear input is converted to feet before the area is calculated, so the square footage output stays correct either way.
A 12 ft × 10 ft bedroom being floored, with a 10% waste allowance and material at $4.50 per square foot:
Flooring is sold by the box, so round 132 sq ft up to whole boxes — at 24 sq ft per box that is six boxes, or 144 sq ft.
Most rooms are not clean rectangles. The reliable method is to divide and add: sketch the floor, split it into rectangles, circles, and triangles that meet without overlapping, calculate each one here, and total the results. An L-shaped living room is two rectangles. A bay window is a rectangle plus a triangle at each side.
Measure at floor level rather than at waist height — baseboards, bowed walls, and out-of-square corners all shift the number. Take each measurement twice, and if the two readings disagree, use the larger one.
Measure the length and the width of the room in feet, then multiply them together. A room 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. If your measurements include inches, convert the inches to a decimal first by dividing by 12 — 12 feet 6 inches becomes 12.5 feet. For rooms that are not a simple rectangle, split the floor into rectangles, calculate each one separately, and add the results together.
One square yard equals nine square feet, because a yard is three feet on each side and 3 × 3 = 9. This conversion matters most when buying carpet, which US suppliers often price per square yard even though rooms are measured in square feet. To convert, divide your square footage by nine — 450 square feet is 450 ÷ 9 = 50 square yards.
For most flooring, tile, and paint jobs, 10 percent is the standard allowance, covering off-cuts, breakage, and mistakes. Add 15 percent for diagonal or herringbone layouts, patterned material that needs alignment, or rooms with many angles and alcoves. Use 5 percent only for a plain rectangular room with a simple layout and material you can reorder easily.
For a material estimate, measure only the floor you actually intend to cover, so closets count if you are flooring them and hallways count if they connect. For a real estate listing, US convention follows ANSI Z765, which measures gross living area from the exterior wall faces, includes interior walls and hallways, and excludes any space with a ceiling under seven feet or areas below grade. The two numbers will not match, and they are not supposed to.
For a circle, take the radius — half the diameter — square it, and multiply by 3.14159. A round patio 10 feet across has a radius of 5 feet, so the area is 5 × 5 × 3.14159 = 78.5 square feet. For a triangle, multiply the base by the perpendicular height and divide by two. A triangular section with an 8-foot base and 6-foot height is (8 × 6) ÷ 2 = 24 square feet.
One acre is 43,560 square feet. The number comes from the old English measure of a chain by a furlong — 66 feet by 660 feet — which is why it looks arbitrary. For a quick reference, a square acre is roughly 209 feet on each side, and a standard American football field including both end zones is about 1.32 acres.
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