Square Footage Calculator
Estimate surface area in square feet and square meters for a room, floor, wall, or other surface. Calculate common shapes, combine several spaces, and add a clearly separated material-waste allowance.
Add a room or surface
Area summary
Add a measured room or surface to see its area and running total.
Formula and example
Rectangle: length × width. Triangle: base × height ÷ 2. Circle: π × radius². Trapezoid: (parallel side A + parallel side B) × height ÷ 2. Each measurement is converted to meters before areas are totaled.
Example: A rectangular room 12 ft by 10 ft has an area of 120 sq ft (about 11.15 m²). With 10% extra material, the estimate is 132 sq ft; the measured area remains 120 sq ft.
How to use this calculator
- Choose a shape and the unit for its dimensions, then enter each positive measurement.
- Optionally name the room and adjust the waste allowance, then add the surface to the total.
- Repeat for more rooms. Remove any row you do not need, or reset to start over.
- Copy the measured total and separate material estimate when finished.
Frequently asked questions
Can I combine rooms measured in different units?
Yes. Each surface is normalized to square meters before it is added, so you can use feet, inches, meters, or centimeters for different entries.
Does the waste allowance change the measured area?
No. It adds a separate estimate for purchasing materials. The calculated surface area remains unchanged.
How much extra material should I allow?
The right allowance depends on the material, layout, and cutting pattern. The default 10% is only a starting estimate; use a percentage recommended by your installer or supplier.