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Calculate square footage for multiple rooms and shapes. Built for contractors and architects. Supports rectangular, square, and circular spaces.
Calculator inputs
Enter measured project values. Results update only when you choose Calculate.
Method
Every downstream takeoff hangs off this number. A 1,200 SF kitchen renovation pulls flooring (12.5 percent waste on tile), paint (350 to 400 SF per gallon at one coat), drywall (38 sheets at 4x12), insulation, and trim — and a 5 percent error in the base square footage shows up in five different material orders. Get the area math right once, and the rest of the takeoff stays clean.
For commercial work, ANSI/BOMA Z65.1 defines how to measure rentable area, useable area, and gross area on plans — they are not interchangeable. For residential, the ANSI Z765 standard governs how square footage is reported in MLS listings. Knowing which definition you owe the client matters as much as the multiplication.
Draw the room or elevation freehand on graph paper before you tape anything. Decompose into rectangles, triangles, and the occasional circle — bay windows, alcoves, and chase walls all become separate shapes you can audit later.
For walls, measure to the finished face of drywall (or the dominant face on commercial plans). For floors, measure inside-of-finish to inside-of-finish. Mixing rough framing dimensions and finished dimensions in one takeoff produces a 1 to 2 percent error in every line.
Rectangle: L x W. Triangle: 0.5 x B x H. Circle: pi x r squared. Add included shapes; subtract openings, voids, and material-changes (a 5x10 tile inset in a hardwood floor is two takeoffs, not one).
Tile and stone: 10 to 15 percent (more on diagonal patterns). LVP and laminate: 7 to 10 percent. Hardwood: 5 to 8 percent. Drywall: 10 to 12 percent. Paint: typically 5 percent for trim cuts, none for wall area.
Split it into two rectangles, calculate each, and add them. A 12 x 16 room with a 4 x 6 alcove is 192 + 24 = 216 SF. The same answer comes from treating the full envelope (16 x 18 = 288) and subtracting the missing corner (12 x 6 = 72). Either method works; pick the one that matches your sketch.
Almost always one of three things: the waste factor was for a low-cut pattern but the actual job has heavy cuts, the takeoff missed transitions and reducers, or the order rounded down to the nearest box instead of up. Run a five-minute audit before placing the order.
Perimeter times wall height, then subtract door and large window openings. Most painters do not subtract small openings (single doors, switch boxes, registers) because the cuts and edge work absorb the offcuts anyway.
Gross area is measured to the outside face of exterior walls and includes everything inside (corridors, mechanical, lobby). Net area excludes those common spaces and shows only the tenant or program area. Always confirm which one the spec is asking for before quoting.
Separate plan workflow
This calculator solves one bounded formula from the inputs shown. BuildVision AI supports reviewed plan takeoff, complete-document CSV, and editable quote lines; the estimator owns pricing and final bid approval.