Square Footage Calculator
Measure area in square feet, metres or yards for any room shape, plus material cost.
About Square Footage Calculator
Area is calculated for the chosen shape in the specified input unit, then converted to square feet (and optionally square metres and square yards). A waste factor is applied to account for cuts and spoilage — standard recommendations are 10% for straight-lay floors, 15% for diagonal or herringbone patterns. If a per-square-foot material cost is entered, the total cost estimate includes the waste allowance.
Formulas
Rectangle
Area = Length × Width
Circle
Area = π × radius²
Triangle
Area = ½ × base × height
Area with waste
Total area = net area × rooms × (1 + waste%)
- n
- Number of rooms
- w
- Waste percentage
Worked example
With the default values below, Square Footage Calculator returns Square Footage (with waste) of 132.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Shapeone of Rectangle / Square, Circle, Triangle, L-Shape (two rectangles)
- Rectangle / Square
- Input Unitsone of Feet (ft), Inches (in), Yards (yd), Metres (m), Centimetres (cm)
- Feet (ft)
- Lengthminimum 0.001
- 12
- Widthminimum 0.001
- 10
- Length (2nd rectangle)minimum 0.001
- 6
- Width (2nd rectangle)minimum 0.001
- 5
- Radiusminimum 0.001
- 6
- Baseminimum 0.001
- 12
- Heightminimum 0.001
- 8
- Number of Rooms / Identical Areasminimum 1
- 1
- Material Cost per sq ftminimum 0 $
- 0 $
- Waste Factoraccepts 0–50 %
- 10 %
Results
- Square Footage (with waste)
- 132.00 sq ft
- Square Footage (net)
- 120.00 sq ft
- Square Metres
- 12.26 m²
- Square Yards
- 14.67 sq yd
Step by step
- 1Single area= 120.00 sq ft
- 2Add 10% waste= 132.00 sq ft
- 3Convert to sq metres= 12.26 m²
Assumptions and limits
- The result is derived only from the 12 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How do I measure an L-shaped room?
Select 'L-Shape' and measure the two rectangles that make up the L. Enter each rectangle's length and width and the calculator adds the areas.
What waste factor should I use for flooring?
10% for straight-lay patterns, 15% for diagonal or herringbone. For tile, 10–15% depending on cut complexity. The waste is built into the 'with waste' figure used for the material cost estimate.
Can I switch between feet and metres?
Yes — select your input unit (feet, inches, yards, metres, centimetres). The result is always shown in square feet and converted to square metres and square yards automatically.
How do I calculate paint coverage?
Measure the walls as rectangles. Most paint covers 350–400 sq ft per gallon. Divide your total wall area by the coverage rate to get gallons needed.