Square footage calculator
Calculate one area or combine several spaces, convert units automatically, add material waste, and estimate cost.
Project total
Add each area above, then apply an optional material allowance and price per square foot.
Calculate a shape and choose “Add to project.”
How to calculate square footage
Convert every linear measurement to feet, apply the formula for the shape, and express the result in square feet. Add separate shapes for an irregular floor plan.
Rectangle or square
area = length × widthMultiply length by width after both are converted to feet. For a square, multiply the side by itself.
Triangle
area = base × height ÷ 2Use the perpendicular height from the base. A sloped side is not the height unless it meets the base at 90 degrees.
Circle
area = π × radius²Square the radius and multiply by pi. If you measured the full diameter, divide it by two first.
Project total
sum of areas × (1 + waste %)Add the measured areas, then apply an optional allowance. Cost equals the final square footage multiplied by price per square foot.
Common square-foot conversion factors
Linear units must be converted before multiplication because an area conversion applies in two dimensions.
NIST unit-conversion reference ↗| Area | Equivalent |
|---|---|
| 1 sq ft | 144 sq in |
| 9 sq ft | 1 sq yd |
| 1 sq ft | 0.09290304 m² |
| 43,560 sq ft | 1 acre |
Square footage examples for common projects
These examples show the calculation path. Replace every measurement, allowance, and price with values from your own project.
Rectangular room
A room measuring 15 ft by 12 ft has 15 × 12 = 180 square feet.
15 ft × 12 ft = 180 sq ftFlooring with an allowance
For 180 square feet with a 10% material allowance: 180 × 1.10 = 198 square feet.
180 × 1.10 = 198 sq ftUse the project calculator →Triangular section
A triangle with a 14 ft base and 8 ft perpendicular height has 14 × 8 ÷ 2 = 56 square feet.
14 × 8 ÷ 2 = 56 sq ftCircular area
A circle with a 6 ft radius has π × 6² ≈ 113.10 square feet.
π × 6² ≈ 113.10 sq ftMeasuring an irregular room
- Sketch the outline and divide it into rectangles, triangles, or circles.
- Measure each shape using the same reference points.
- Calculate each section and add it to the project list.
- Subtract excluded openings only when your material estimate requires it.
Before ordering material
- Measure twice and note every unit.
- Confirm whether products are sold by square foot, box, roll, sheet, or piece.
- Use a waste allowance suitable for the material, pattern, cuts, and installer.
- Account separately for labor, delivery, tax, and fixed project fees.
Square footage calculator FAQ
How do I calculate square footage?
For a rectangle, convert length and width to feet and multiply them. A 12-foot by 10-foot room is 120 square feet. Use the appropriate formula for triangles or circles.
How do I calculate square footage when measurements include inches?
Divide inches by 12 to convert them to feet, then use the area formula. This calculator can accept inches directly and performs the conversion before calculating area.
How do I calculate an irregular room?
Divide the floor plan into simple rectangles, triangles, or circles. Calculate each section, add it to the project list, and use the combined total. Subtract excluded areas only when appropriate for the material.
What waste percentage should I add?
There is no universal percentage. The right allowance depends on the material, pattern, room shape, cuts, defects, replacement stock, and installer requirements. Confirm the allowance with the manufacturer, supplier, or contractor.
How is material cost estimated?
The calculator multiplies square footage after the optional waste allowance by the entered material price per square foot. It does not include tax, delivery, labor, tools, fixed fees, or package rounding.
What is the difference between square feet and linear feet?
A linear foot measures one-dimensional length. A square foot measures two-dimensional area. A surface that is 1 foot long and 1 foot wide covers 1 square foot.
How many square feet are in a square yard or acre?
One square yard equals 9 square feet. One acre equals 43,560 square feet.
Does quantity multiply the area?
Yes. Quantity multiplies the calculated area for identical rooms, panels, or sections before that line is added to the project total.
Are the results exact?
The formulas and unit factors are applied consistently, but a practical result is only as accurate as the measurements entered. Product coverage, installation rules, package sizes, and on-site conditions can change purchasing needs.
Are my project measurements saved?
No project values are transmitted or stored by this plugin. Calculations and the project list remain in the current browser page and reset when the page is reloaded.
Planning note: Results depend on the measurements and assumptions entered. Verify site dimensions, product coverage, package rounding, waste requirements, prices, and installation specifications before purchasing materials or preparing a quote.