Measure any rectangular area in square feet — flooring, paint, sod, and more. Free with steps.
Flooring, paint, sod, tile, and roofing are all bought by the square foot — the area of a 12-inch by 12-inch square. A 12 ft by 10 ft room is 120 square feet of floor, full stop. Our free Square Footage Calculator multiplies your length and width, converts the answer into square inches, square yards, square meters, and acres, and adds the 10% waste allowance that flooring and tile installers actually order.
Square footage is also the denominator of real estate. Home prices, rents, and renovation budgets are quoted per square foot, which makes accurate area math worth real money: a 100 ft² measurement error on a $400/ft² home is $40,000 of phantom value. Appraisers follow strict ANSI standards for what counts — above-grade, finished, heated space — but the underlying multiplication is the same one this calculator performs.
Measure in feet, inches, yards, or meters; the tool normalizes to feet. For L-shaped or irregular rooms, split the floor into rectangles, run each through the calculator, and add the results.
A square foot (ft²) is the area of a square measuring one foot per side — 144 square inches. It is the standard US unit for floor area, wall area, and material quantities. Nine square feet make a square yard (the carpet unit); 43,560 square feet make an acre (the land unit).
Area scales with the square of linear size: doubling each side quadruples the area. A 10 × 10 ft room is 100 ft²; a 20 × 20 ft room is 400 ft², not 200. This quadratic scaling is why paint and flooring estimates blow up faster than room dimensions suggest — and why measuring carefully pays off.
The professional’s constant companion is the waste factor: 10% for flooring and tile (cuts around doors and closets), 10–15% for roofing (hips, valleys, starter courses), 5% for sod (it cuts cleanly). Ordering the exact net area guarantees a mid-job trip to the store; the calculator’s waste line exists so you order once.
Key terms:
For rooms that are not rectangles, divide the floor into rectangles (and right triangles, A = ½bh), compute each, and add. Closets under 2 ft deep are often deducted from flooring but included in paint — know your trade’s convention.
A bedroom measures 12 ft by 10 ft. How much laminate flooring?
Order 7 boxes (140 ft²). The half-box remainder becomes closet cuts and future repairs — keep a box, not a plank.
A feature wall is 150 inches wide and 96 inches tall. How many square feet of shiplap?
Order 110 ft² of shiplap. Deduct 21 ft² if a 3 × 7 ft doorway interrupts the wall.
The Alvarez family is comparing flooring bids for their 1,600 ft² home. Their room-by-room takeoff: living 320, kitchen 180, three bedrooms 150/140/130, two baths 60/55, hallway 90, laundry 70 — summing to 1,195 ft² of floor. (Garage and patios excluded.) At 10% waste, the order is 1,315 ft². Bid A quotes $6.50/ft² installed on the order quantity: $8,548. Bid B quotes $5.90/ft² but on a “generous” 1,500 ft² estimate: $8,850. The per-foot price misleads; the takeoff reveals Bid A is cheaper despite the higher rate.
The same takeoff prices the paint. Wall area runs roughly 3–3.5× floor area for 8-foot ceilings with normal openings: about 4,000 ft² of wall. At 350 ft² per gallon, that is 12 gallons per coat, 24 for two coats — and suddenly the $45/gallon versus $30/gallon decision is a $360 swing. Square footage turns vague “whole house” quotes into line items you can actually compare.
A second scenario: sod for a new lawn. The yard is 60 ft by 40 ft (2,400 ft²) minus the 800 ft² house footprint and 300 ft² of beds and paths: 1,300 ft² net. Sod wastes only ~5% (it cuts with a knife): order 1,365 ft², and pallets at 500 ft² each mean three pallets with 135 ft² to spare for the parkway strip everyone forgets.
The ANSI Z765 standard governs what counts as square footage in US appraisals: finished, above-grade, heated, and directly accessible living area, measured to the outside of exterior walls. A 2,000 ft² listing might appraise at 1,700 if 300 feet are a below-grade “bonus room” — and since appraisals anchor mortgages, that 300 ft² fiction can kill a closing. The calculator’s math is trivial; the standard defining the outline is the valuable part.
Building codes use square footage as a safety denominator. Occupant load (one person per 15 ft² in assembly spaces), egress width, sprinkler design, and ventilation rates all key off floor area. A restaurant’s 1,500 ft² dining room legally holds 100 people; the same room at 1,200 ft² holds 80. Owners who “find” extra square footage in a remodel sometimes find the fire marshal instead.
Tax assessors, meanwhile, tax what they can measure from the street — footprint times stories — which is why additions without permits create assessment gaps that surface at sale. And property tax per square foot varies wildly: $2/ft²/year in rural counties versus $20+ in Manhattan. Area is the one input every property formula shares.
On the material side, the industry’s quiet revolution is the waste audit. Large flooring contractors now track offcut percentages per crew and per product; crews running 14% waste on a 10% bid lose the margin. The humble L × W, aggregated across a year of jobs, becomes a profitability dashboard — proof that square footage is never just geometry.
Square footage = length × width in feet (A = L×W). Conversions: 1 ft² = 144 in² = 1/9 yd² ≈ 0.0929 m²; 43,560 ft² = 1 acre. Order quantity ≈ net × 1.10 (flooring/tile), 1.05 (sod), 1.10–1.15 (roofing). Split irregular rooms into rectangles. Source: Sigma Calculator, Square Footage Calculator, https://sigmacalculator.net/math-calculators/square-footage-calculator/
Cite this page as: Square Footage Calculator, Sigma Calculator, https://sigmacalculator.net/math-calculators/square-footage-calculator/
Last updated: October 12, 2026