Square footage
calculator.
Measure a room in feet and inches, or meters and centimeters, and get its area in square feet, square meters, square yards and acres. Rectangles, L-shapes, triangles, circles and trapezoids are built in, and you can add a closet or subtract an island.
The rectangle is 125 sq ft (11.61 m²).
- Square feet
- 125 sq ft
- Square meters
- 11.61 m²
- Square yards
- 13.89 sq yd
- Acres
- 0.00287 acres
A = length × width = 12.5 ft × 10 ft = 125 sq ft; ÷ 9 = 13.89 sq yd; × 0.09290304 = 11.61 m²Length times width,
and every other shape.
- Feet and inches are combined first (12 ft 6 in = 12.5 ft), then the shape's area formula is applied. Inches must be under 12 and centimeters under 100.
- Conversions use the exact definitions in NIST Handbook 44: 1 ft = 0.3048 m, so 1 sq ft = 0.09290304 m²; 1 sq yd = 9 sq ft; 1 acre = 43,560 sq ft.
- Extra areas are rectangles added to or subtracted from the main shape. The subtracted total cannot be larger than the rest.
- Results are shown to two decimal places; the calculation keeps full precision until then. Cost is area × price in the unit you choose.
How do you calculate square footage?
Multiply the length by the width, both in feet. A room 12 ft 6 in by 10 ft is 12.5 × 10 = 125 sq ft. Convert inches to feet by dividing by 12 before you multiply: 6 in is 0.5 ft, 3 in is 0.25 ft and 9 in is 0.75 ft. Multiplying 12.6 by 10 instead would be wrong, because 6 inches is not 0.6 ft.
area (sq ft) = length (ft) × width (ft)
feet = whole feet + inches ÷ 12How do you find the square footage of an L-shaped room?
Split the L into two rectangles that do not overlap, find each area, and add them. A living area 20 ft by 12 ft with a dining nook 10 ft by 8 ft is 240 + 80 = 320 sq ft. Make sure the second rectangle starts where the first ends, or the shared corner is counted twice. Any room made of rectangles works the same way; add each closet or bay as an extra area.
How do you calculate the area of a triangle, circle or trapezoid?
A triangle is base × height ÷ 2, where the height is measured square to the base: 12 ft by 8 ft is 48 sq ft. If you can only measure the three sides, Heron's formula gives the area: sides of 10, 12 and 14 ft make s = 18 and √(18 × 8 × 6 × 4) = 58.79 sq ft.
A circle is π × diameter² ÷ 4: a round patio 10 ft across is 78.54 sq ft. A trapezoid, such as a bay or an angled corner, is the average of the two parallel sides times the distance between them: (10 + 14) ÷ 2 × 8 = 96 sq ft.
triangle = base × height ÷ 2
circle = π × d² ÷ 4
trapezoid = (a + b) ÷ 2 × hHow do you convert square feet to square meters, square yards or acres?
Multiply square feet by 0.09290304 for square meters; this factor is exact because the foot is defined as exactly 0.3048 m. Divide by 9 for square yards and by 43,560 for acres. So 125 sq ft is 11.61 m², 13.89 sq yd and 0.00287 acres. Going the other way, 1 m² is about 10.764 sq ft. Rounding the factor to 10.76 understates a 2,000 sq ft house by about 0.7 sq ft.
m² = sq ft × 0.09290304
sq yd = sq ft ÷ 9
acres = sq ft ÷ 43,560How do you subtract an area you do not need?
Find the area of the whole space, then subtract the part that will not be covered. A 12 by 10 ft kitchen is 120 sq ft; with a 4 by 3 ft pantry added and a 2 ft 6 in by 2 ft built-in removed, the floor to cover is 120 + 12 − 5 = 127 sq ft. For flooring, tile or paint you then add a waste allowance on top of this net area.
How do you work out the cost from square footage?
Multiply the area by the price per square foot. 125 sq ft at $4.00 per sq ft is $500.00. If the price is per square yard, as carpet often is, divide the square feet by 9 first: 125 ÷ 9 × $36.00 is also $500.00. The calculator accepts prices per square foot, square yard or square meter.
Worked examples.
A bedroom in feet and inches
A room 12 ft 6 in long and 10 ft wide.
125 sq ft (11.61 m², 13.89 sq yd).
Load this exampleAn L-shaped living and dining area
A 20 by 12 ft living area joined to a 10 by 8 ft dining nook.
320 sq ft.
Load this exampleA room in meters
A room 4 m 50 cm by 3 m.
13.5 m², which is 145.31 sq ft.
Load this exampleKitchen with a pantry, minus a built-in
A 12 by 10 ft kitchen, plus a 4 by 3 ft pantry, minus a 2 ft 6 in by 2 ft built-in cabinet.
127 sq ft of floor.
Load this exampleA round patio with a price
A circular patio 10 ft across, priced at $12 per square foot.
78.54 sq ft, about $942.48.
Load this exampleA triangular garden bed by its sides
A corner bed with sides of 10, 12 and 14 ft.
58.79 sq ft.
Load this exampleWhat this calculator
does not do.
- It covers flat, horizontal areas. Sloped ceilings, roofs and stairs need their own measurements.
- Curved walls other than a full circle must be approximated with the shapes provided.
- It does not apply any real-estate measurement standard. Listed home square footage follows local rules about walls, stairs and unfinished space.
- Extra areas are rectangles only; split other shapes into rectangles, or calculate them separately.
Common questions.
How many square feet is a 12 by 12 room?
144 sq ft: 12 × 12 = 144. That is 16 sq yd or 13.38 m².
How do I convert inches to feet for square footage?
Divide the inches by 12 and add them to the feet. 10 ft 9 in is 10.75 ft, so a 10 ft 9 in by 12 ft room is 129 sq ft.
How many square feet are in an acre?
Exactly 43,560 sq ft. A plot 660 ft by 66 ft is one acre. An acre is about 4,046.86 m².
How many square feet are in a square meter?
About 10.764 sq ft. The exact relation is 1 sq ft = 0.09290304 m², so 1 m² = 1 ÷ 0.09290304 = 10.7639… sq ft.
Should I include closets?
For flooring, yes, if the floor runs into them; add each one as an extra area. Subtract anything permanently fixed that the floor will not go under, such as a kitchen island.
- NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement — 1 international foot = 0.3048 m exactly; 1 sq yd = 9 sq ft; 1 acre = 43,560 sq ft exactly; 1 sq ft = 929.0304 cm² exactly
- NIST SP 811, Appendix B.9: Factors for units listed by kind of quantity — square foot to square meter 9.290 304 E-02 and foot to meter 3.048 E-01, both marked exact
Feet and inches (or meters and centimeters) are combined into one length, the shape's area formula is applied in the units you measured in, and the result is converted with NIST's exact factors. The three-sided triangle uses Heron's formula in Kahan's numerically stable form. Tests check hand-worked vectors for every shape, the exact acre and hectare relations, 300 random rooms measured in both feet and meters, right triangles by three sides against half the rectangle, and every input error.
Built and reviewed by CalculatorLab against the sources above; every worked example on this page is re-checked by our automated test suite before each release. How we build and check calculators. Found a problem? Tell us.