Square Footage Calculator
Rooms ยท Shapes ยท Waste ยท Material cost
โฌ Enter dimensions to calculate square footage and order quantity.
Square Footage Formulas
Square footage is area expressed in square feet. Convert every length to feet first, then apply the shape formula.
Rectangle
Circle, triangle, trapezoid
Waste and cost
Conversion Reference
| From | To | Factor |
|---|---|---|
| 1 sq ft | sq meters | 0.09290304 |
| 1 sq yd | sq ft | 9 |
| 1 acre | sq ft | 43,560 |
| 1 ft | meters | 0.3048 |
| 1 in | ft | 1/12 |
Factors use the international foot (exactly 0.3048 m) as published in NIST conversion guidance.
How to Use This Square Footage Calculator
Pick the shape that matches the space. Enter length and width in feet and optional inches, or switch to meters. Add a waste percent when ordering flooring or tile, and enter price per square foot for a material cost estimate.
Multi room mode adds several rectangles for a whole floor plan. Results show net area, waste overage, order quantity, square yards, square meters, acres, and cost.
What square footage means
Square footage is the two dimensional area of a floor, wall, patio, or lot measured in square feet. Real estate listings, flooring quotes, and paint estimates often use this unit in the United States.
How to calculate square footage manually
1. Measure length and width. 2. Convert inches to feet (inches รท 12). 3. Multiply. Worked example: a room is 12 ft 6 in by 10 ft 3 in. Length = 12 + 6/12 = 12.5 ft. Width = 10 + 3/12 = 10.25 ft. Area = 12.5 ร 10.25 = 128.125 sq ft.
L shaped rooms
Split the L into two rectangles along the inside corner. Example: a 20ร12 rectangle plus an 8ร10 rectangle equals 240 + 80 = 320 sq ft. Alternatively, take a 20ร22 outer box and subtract the missing 12ร10 cutout: 440 โ 120 = 320 sq ft.
Waste factor for flooring
Order quantity = measured area ร (1 + waste%). Common planning ranges are about 5 to 10% for a simple straight lay, about 15% for diagonal layouts, and about 20% for herringbone or highly cut rooms. These are installer planning ranges, not a single legal standard. Round up to whole boxes from the same dye lot.
Material cost
Multiply order square footage by price per square foot. Example: 132 sq ft ordered ร $4.50 = $594 before tax, underlayment, and labor. Carpet sold by the square yard uses order sq ft รท 9.
Common mistakes
- Multiplying feet by inches without converting
- Double counting the corner of an L shape
- Ordering exact net area with no waste
- Using wall height when you need floor area
- Mixing meters and feet in one product
Practical scenarios
Homeowners size laminate or LVP. Renters check whether a rug fits. Landscapers estimate sod. Painters convert wall rectangles after subtracting doors. Agents sanity check listed living area against simple room sums (official living area rules can differ).
When this calculator is useful
Use it for room floors, patios, circular beds, triangular corners, trapezoid lots, L kitchens, and multi room material takeoffs.
When this calculator may not be enough
It does not replace ANSI/BOMA commercial measurement standards, appraisal living area rules, or a contractor takeoff for curved walls and stairs. Complex plans need scaled drawings.
How to interpret your result
Net sq ft is the measured area. Order sq ft includes waste. Cost uses your price on the order quantity. Square meters use the NIST international foot conversion.
Walls versus floors
Floor area uses length ร width. Wall paint area uses length ร height for each wall, then subtract openings. Use rectangle mode with height as the second dimension for a single wall.
Circle and triangle notes
Circle area uses ฯrยฒ with r = diameter รท 2. Triangle height must be perpendicular to the base, not a sloped side length.
Measuring tips that change the result
Measure along the floor at the longest wall lines, not the baseboard face if trim reduces usable floor. For flooring that stops at a doorway, measure only the floor you will cover. Closets count when the material continues inside them.
Tape measure bows and phone AR tools can drift by an inch or more. When a room is out of square, measure both opposite walls and use the larger span if you need material coverage rather than a tight fit estimate.
Boxes, rolls, and round up rules
After you have order square footage, divide by the coverage printed on the box or roll and round up to a whole package. Keep one spare package from the same lot for repairs. Do not mix dye lots across a visible floor if you can avoid it.
Paint versus flooring square footage
Flooring uses length times width. Interior paint often needs wall area: perimeter wall lengths times ceiling height, minus doors and large windows. A 12 by 10 room with 8 ft ceilings is not 120 sq ft of paint. It is closer to the sum of four wall rectangles after openings.
Acre and lot context
One acre equals 43,560 square feet. A half acre is 21,780 sq ft. This calculator reports acres for large outdoor areas, but land surveys use boundary geometry that may not match a simple rectangle on a sketch.
Limitations
Results assume flat rectangular style geometry and the dimensions you enter. Irregular curves, stairs, and built ins need extra measurement. Cost excludes tax, labor, and adhesives.
Frequently Asked Questions
Sources & References
- NIST Guide to the SI (SP 811), Appendix B conversion factors: nist.gov/pml/special-publication-811
- NIST SP 811 overview: nist.gov/pml/special-publication-811