Square Footage Calculator
Find the square footage of rectangles, circles, triangles, and border/frame areas — with square-meter conversion and an optional material cost estimate.
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Adjust the inputs on the left to see your square footage.
Square footage is the standard US measure of area for rooms, flooring, paint, lawns, and real estate listings. Measure your dimensions in feet, pick the shape, and the calculator returns the area in square feet (and square meters), multiplied by however many identical sections you have — plus a cost estimate if you enter a price per square foot.
How it's calculated
Rectangle : L × W
Circle : π × (D ÷ 2)² (L is the diameter)
Triangle : ½ × base × height
Border : (L + 2b) × (W + 2b) − (L × W)
Total : area × quantity
Metric : 1 sq ft = 0.09290304 m²
Cost : total sq ft × price per sq ft
The border shape computes the area of a band of width b that wraps around an L × W inner area — think a sidewalk around a pool, a mulch ring around a garden bed, or a frame around a deck. It is the outer rectangle minus the inner one, so only the band itself is counted.
Irregular rooms. Most US homes aren't perfect rectangles. Split an L-shaped or odd room into rectangles and triangles, calculate each section, and add them up — the quantity slider helps when several sections are identical.
Buying material. Contractors typically add a waste factor on top of the measured area: about 5–10% for flooring and paint, and 10–15% for tile laid diagonally or patterned carpet. Boxed materials are sold in whole units, so round up to the next full box.
Assumptions and limitations. All inputs are interpreted in feet and results in square feet; the border-width slider only affects the border shape. The cost estimate is materials only — it excludes labor, underlayment, removal, and sales tax, which vary widely by region. For paint coverage by gallon or tile counts by box, use the dedicated paint and carpet/tile calculators.
Frequently asked questions
How do I calculate the square footage of a room?
Measure the length and width in feet and multiply them: a 12 ft × 10 ft room is 120 sq ft. For L-shaped rooms, split the space into rectangles, calculate each, and add the results.
How many square feet are in a square meter?
1 square meter = 10.764 square feet, and 1 square foot = 0.0929 square meters. The calculator converts automatically.
How does the border / frame shape work?
It calculates the area of a band of constant width around an inner L × W area — outer rectangle minus inner rectangle. A 3 ft border around a 12 × 10 ft area is (18 × 16) − 120 = 168 sq ft.
How much extra material should I buy for waste?
Add roughly 5–10% for standard flooring and paint jobs, and 10–15% for diagonal tile layouts or patterned material that needs matching. Always round up to whole boxes or gallons.
Is square footage measured the same way for real estate?
Listings usually report finished, heated living area measured from exterior walls, and rules vary by state and appraiser. This calculator measures plain geometric area, which is what you need for materials.