Square Footage Calculator
The first number on almost every estimate — area, in square feet, square yards, and square meters, for rectangles, triangles, circles, trapezoids, and whole rooms.
Measure twice, in feet and inches converted honestly (6 inches is 0.5 ft, not 0.6). Odd-shaped spaces: split them into rectangles and triangles and add the pieces — that is all any estimator does.
How the math works
Rectangle: length × width. Triangle: base × height ÷ 2 — the height is measured perpendicular to the base, not along the slope. Circle: π × radius² (radius is half the diameter you measured). Trapezoid: add the two parallel sides, halve the sum, multiply by the distance between them. A room is a rectangle floor plus four walls: wall area is the perimeter — 2 × (length + width) — times the ceiling height.
Square yards are square feet ÷ 9. Square meters are square feet × 0.0929. Flooring, tile, drywall, paint, and sod are all sold off this one number, which is why every calculator in this suite either starts here or does this math inside itself.
A worked example
A 12 ft × 14 ft bedroom floor: 12 × 14 = 168 sq ft. That is 18.67 sq yd of carpet or 15.61 m² on a metric plan. Run it above — the calculator agrees, and now the flooring, paint, and drywall numbers for the same room all trace back to it.
Questions from the field
How do I measure an L-shaped room? Split it into two rectangles, measure each, and add. Every irregular space on a real job is measured this way — nobody has a formula for your floor plan, and they do not need one.
How many square feet is a 20 × 20 room? 400 sq ft of floor. The walls at 8 ft ceilings are 640 sq ft gross — 2 × (20 + 20) × 8 — before doors and windows come out.
Do I subtract doors and windows? For paint, yes — a standard door is about 21 sq ft, a window about 15 (the paint calculator here does it for you). For drywall and flooring takeoffs, most estimators leave openings in and let the waste factor absorb them.
What does cost per square foot actually include? Whatever the person quoting it says it includes — which is why it is a comparison tool, not a price. In Long Beach, whole-scope remodel work and ADU builds are routinely compared on a $/sq ft basis; the Long Beach ADU cost guide shows what those numbers are made of locally.
The other field calculators
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