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Square Footage Calculator
Add rooms, plots and odd shapes in feet and inches, yards or metres, subtract anything you won't cover, and get the total in square feet, square metres, acres and more — with an optional cost.
Measure wall to wall at floor level. For an irregular room, split it into shapes and add them up; subtract fixed islands, columns or built-ins you won't cover.
How it's calculated
- Rectangle · L-shapelength × width · (l₁ × w₁) + (l₂ × w₂)
- Circle · half circleπ × (d ÷ 2)² · π × (d ÷ 2)² ÷ 2
- Trianglebase × height ÷ 2 · √(s(s − a)(s − b)(s − c)), s = (a + b + c) ÷ 2
- Trapezoid(a + b) ÷ 2 × height
- TotalΣ added − Σ subtracted, × (1 + waste %)
Exact definitions: 1 ft = 0.3048 m, 1 in = 2.54 cm, 1 yd = 0.9144 m, so 1 sq ft = 0.09290304 m². 1 acre = 43,560 sq ft = 4,046.8564224 m²; 1 hectare = 10,000 m².
Worked example
A 12 × 10 ft kitchen (120 sq ft) with a 6 × 5 ft breakfast nook (30 sq ft), minus a 6 × 3 ft island (18 sq ft), is 120 + 30 − 18 = 132 sq ft = 12.263 m².
With 10% extra for cuts that's 145.2 sq ft of flooring; at $4 per sq ft, $580.8.
Frequently asked questions
How do I calculate square footage?+
For a rectangle, multiply length by width in feet: a 12 × 10 ft room is 120 sq ft. For an L-shaped or irregular room, split it into rectangles and other simple shapes, work out each one and add them up.
How do I convert square feet to square metres?+
Multiply by 0.09290304 (because 1 ft = 0.3048 m exactly, and 0.3048² = 0.09290304). 120 sq ft is 11.15 m². To go the other way, multiply square metres by about 10.7639.
How do I measure a room with inches?+
Type feet and inches together, for example 12' 6" or 12 6 — the calculator turns 6 inches into half a foot. Or switch the unit to inches: 150 × 120 in is 18,000 sq in, which is 125 sq ft (144 sq in to a square foot).
How do I find the area of a circle or half circle?+
π × radius², where the radius is half the diameter. A 10 ft circle is π × 5² = 78.54 sq ft; a half circle with a 10 ft straight side is half that, 39.27 sq ft.
How do I find the area of a triangle when I only know the sides?+
Use Heron's formula: s = (a + b + c) ÷ 2, area = √(s(s − a)(s − b)(s − c)). Sides of 13, 14 and 15 ft give s = 21 and an area of 84 sq ft.
How much extra flooring should I buy?+
Flooring makers and installers commonly suggest 5–10% extra for cuts and breakage, and more for diagonal layouts, patterned tile or rooms with many corners. Check the product's instructions.
How many square feet are in an acre?+
43,560 sq ft, which is 4,046.86 m². A hectare is 10,000 m², or about 2.471 acres.
Is anything I enter saved or sent?+
No. Everything is calculated in your browser and nothing is uploaded or stored.