How do I calculate square footage? Find the area of any room or space in square feet, square meters, square yards, and acres. Supports rectangles, triangles, circles, trapezoids, and L-shapes.
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Last updated March 2026 by our expert review team
Dimensions are approximate averages for US residential construction.
Hawkin
Certified Cost & Estimating Professional
AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.
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Licensed Structural Engineer
FISE-certified structural engineer with 11+ years designing bridges, retaining walls, and foundations. MSc from Aalto University.
See full profileUpdated March 2026
How we verify our calculatorsBreak irregular rooms into rectangles and triangles, calculate each, then add them together.
Measure to the nearest inch for accuracy. A 1-inch error on a 20-foot wall changes the area by 1.67 sq ft per foot of width.
Use our Sq Ft to Linear Ft calculator to convert between square feet and linear feet for flooring conversions.
For real estate, square footage is measured from exterior walls. Interior measurements will be 10 to 15% smaller.
After measuring your area, use our flooring calculator to estimate materials for tile, hardwood, or laminate.
1 acre = 43,560 sq ft. A standard residential lot is 0.15 to 0.25 acres.
For electrical work, use our conduit fill calculator to size conduit runs per NEC code.
Select a shape and enter your measurements in feet or meters.
The calculator applies the correct formula for your shape to find the area.
Results are converted to sq ft, sq m, sq yd, acres, and sq inches with the perimeter.
Formulas by Shape
Rectangle: Area = Length x Width
Triangle: Area = 0.5 x Base x Height
Circle: Area = pi x (Diameter / 2) squared
Trapezoid: Area = 0.5 x (Side A + Side B) x Height
L-Shape: Area = (L1 x W1) + (L2 x W2)
How do I calculate square footage of a room?
Multiply length by width in feet. A 12 x 15 room is 180 sq ft.
How do I convert sq ft to sq meters?
Multiply sq ft by 0.0929. For example, 200 sq ft = 18.58 sq m.
How many sq ft in an acre?
43,560 sq ft. A football field (excluding end zones) is about 48,000 sq ft or 1.1 acres.
How do I measure an L-shaped room?
Divide it into two rectangles. Measure each rectangle (L x W), calculate the area of each, and add them together.
How do I calculate sq ft of a circle?
Use the formula: area = pi x radius squared. For a 15 ft diameter circle: pi x 7.5 squared = 176.7 sq ft.
What is the square footage of a 12x12 room?
144 sq ft. This is a standard bedroom size.
How do I convert sq ft to sq yards?
Divide sq ft by 9. For example, 270 sq ft = 30 sq yards. Carpet is often sold by the square yard.
How accurate do my measurements need to be?
Measure to the nearest inch. For most home projects, this gives accuracy within 1 to 2% which is adequate for material ordering.
A standard bedroom. Enough space for a queen bed, dresser, and nightstands.
A mid-sized living room suitable for a sectional sofa, coffee table, and entertainment center.
A circular patio that comfortably fits a 6-person dining set with room to walk around.
A common kitchen layout. Divide into two rectangles and add the areas together.
Confusing linear feet with square feet
Linear feet measures one dimension (length). Square feet measures area (length x width). 20 linear feet of a 10-foot-wide room is 200 sq ft.
Forgetting to convert inches to feet
12 x 15 inches is 1.25 sq ft, not 180 sq ft. Divide inches by 12 to get feet before multiplying.
Using interior measurements for real estate
Real estate square footage is measured from exterior walls. Interior measurements are 10 to 15% smaller than what the listing should show.
Not accounting for irregular shapes
Measure and calculate each section separately, then add the areas together. Most rooms can be split into rectangles and triangles.
Rounding too early in the calculation
Calculate with full decimal precision and only round your final answer. Early rounding compounds errors, especially on large areas.
This calculator provides estimates for informational purposes only. Always verify measurements before purchasing materials.