Square Footage Calculator
Floor area
Results
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How to Use This Square Footage Calculator
Floor area math sounds simple until you are standing in an L-shaped kitchen with a tape measure, trying to remember whether you multiply diameter or radius for a round nook. I have watched homeowners buy a full pallet of flooring based on a rough "about 200 square feet" guess—and return half of it two weeks later. This calculator handles the unit conversions and shape formulas so you can quote material orders with confidence.
Select your shape: rectangle, circle, or triangle. Enter each dimension with its own unit dropdown—feet, yards, inches, miles, meters, kilometers, or centimeters. Set quantity if you are tallying multiple identical areas (two matching bedrooms, for example). Results show area in square feet and square meters, plus the formula breakdown so you can spot-check the numbers.
Moving onto practical workflows: measure wall-to-wall for flooring, inside curb for a patio pour, or the flat footprint for a tile job. Once you have square feet, feed that into our BTU Calculator for HVAC sizing or the Roofing Calculator if you know the horizontal projection of the roof.
Square Footage Calculator Formulas and Practical Applications
Rectangle
The workhorse formula for rooms, decks, and rectangular beds:
Area = Length × Width
A 12 ft × 10 ft bedroom is 120 ft². Multiply by quantity for repeated zones.
Circle
Enter diameter and the tool halves it to get radius internally—no need to divide by two yourself:
Area = π × (Diameter ÷ 2)²
Think of a round dining nook or a circular fire pit pad: a 10 ft diameter circle covers about 78.5 ft².
Triangle
Uses base and vertical height (not the sloped side length):
Area = ½ × Base × Height
Handy for gable ends, triangular lawn sections, or any space where you know the base run and peak height.
Standard Units and Conversion Tables
US flooring, paint, and HVAC specs typically use square feet; metric projects use square meters. Quick references:
- 1 ft²: A square 12 inches on each side.
- 1 yd²: 9 ft² (3 ft × 3 ft).
- 1 m²: ≈ 10.764 ft²—the tool converts automatically in results.
- 1 acre: 43,560 ft²—use miles or feet inputs for large parcels if needed.
Each dimension converts independently, so you can enter length in meters and width in feet without manual conversion.
Frequently Asked Questions
How do I measure an L-shaped room?
Split the floor plan into rectangles, calculate each section separately, and add the areas together. Most irregular rooms break down into two or three rectangles faster than trying to force one formula.
Should I use diameter or radius for a circle?
Enter diameter—the full width across the circle. Tape measures naturally span edge to edge, and the calculator converts to radius internally for the πr² formula.
Does this include waste for flooring or tile?
This tool returns exact geometric area. Add 5–15% waste depending on material and layout complexity. Our Tile Calculator includes a built-in waste percentage field for that next step.
Disclaimer. Informational only—not architectural or contractor advice. Measure on site and add waste factors for materials.