About this tool
This square footage calculator finds the floor, wall, lot, or lawn area of any common shape from a few measurements: rectangles and squares, circles from the diameter or radius, triangles from base and height or from three sides, trapezoids, L-shaped rooms as an overall rectangle minus a notch, and ellipses. A running total lets you add up several rooms or oddly shaped sections into one figure, a waste allowance covers cutting loss, and a price per square foot turns the total into a material cost estimate. Every area is shown in square feet, square inches, square yards, square meters, acres, and hectares at once. It is meant for flooring, tile, paint, sod, and mulch shopping, real-estate listings, and anyone who needs to measure a space and convert the result.
How it works
Each shape uses its textbook formula: rectangle length x width; square side²; circle pi x r² with r = diameter / 2; triangle ½ x base x height, or Heron's formula sqrt(s(s-a)(s-b)(s-c)) with s the half-perimeter when three sides are given; trapezoid (a + b) / 2 x height; L-shape overall length x width minus notch length x width; ellipse pi x (long axis / 2) x (short axis / 2). Measurements are taken in the unit you pick and the area is converted with exact factors: 1 sq ft = 144 sq in = 0.09290304 m², 1 sq yd = 9 sq ft, 1 acre = 43,560 sq ft, 1 hectare = 10,000 m². The waste allowance multiplies the total by 1 + waste%, and the cost is that figure times the price per unit area.
Frequently asked questions
How do I calculate the square footage of a room?
Measure the length and width in feet at floor level and multiply them: a 12 ft by 10 ft room is 120 sq ft. Measure to the wall, not the baseboard, and if the room is not a clean rectangle split it into rectangles (or use the L-shape option) and add the pieces with the running total. Closets, alcoves, and bay windows count if they will be floored, and doorways are usually ignored because the flooring runs through them.
How many square feet are in a square yard, a square meter, and an acre?
A square yard is 9 sq ft (3 ft x 3 ft). A square meter is 10.764 sq ft, so 120 sq ft is about 11.15 m². An acre is 43,560 sq ft, roughly 209 ft x 209 ft, and a hectare is 10,000 m² or about 2.47 acres. Carpet is often sold by the square yard and tile by the square foot or square meter, which is why the calculator shows all of them together.
How much extra should I add for waste?
For flooring, tile, and carpet the usual allowance is 10 percent, or 15 percent for diagonal layouts, herringbone, and rooms with many angles, because every cut piece leaves an offcut you cannot reuse. Paint and sod need less, around 5 percent. Enter the percentage in the waste box; the material cost estimate uses the area including waste, which is what you actually have to buy.
How do I measure an irregular or curved area?
Break it into shapes you can measure. A room with a bump-out is a rectangle plus a smaller rectangle; a bay window is often a trapezoid; a rounded patio can be a rectangle plus a half circle (enter the full circle and halve it, or add two quarter-sized pieces). Use the Add to running total button after each piece and the tool sums them. For plots with several straight sides of known length but no right angles, triangles from three sides using Heron's formula work well.