"Length times width" is the formula everyone remembers — and it's the wrong one for a round room, a triangular nook under a staircase, or any space that isn't a plain rectangle.
How to calculate square feet, by shape
This calculator picks the right formula for you: length × width for rectangles, π × radius² for circles (just enter the diameter), and base × height ÷ 2 for triangles.
Square feet of a circle, from a diameter you can actually measure
Measuring a radius on a real room is awkward — measuring straight across (the diameter) is easy. Enter the diameter and this tool halves it and applies the circle formula automatically.
Flooring cost calculator, built in
Enter a price per square foot and the total cost appears alongside the area — useful for a quick flooring, tile, or carpet budget without a separate calculation.
Square yards calculator, since flooring is priced that way
Carpet and some flooring materials are quoted per square yard, not square foot — this shows both automatically, along with acres for larger outdoor areas.
