How to Calculate Square Footage for Flooring Projects

Before you buy a single plank or tile, get the math right. Here's how to measure any room shape and avoid running short mid-project.

Square footage calculation diagram for rectangular and irregular room shapes
Quick Answer

For a rectangular room, square footage equals length times width (both in feet). A 15×12 ft room is 180 square feet. For irregular shapes, divide the space into rectangles, calculate each separately, then add the totals together. Always add 10% extra for waste from cuts and pattern matching.

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Basic Rectangle Formula

Area = Length × Width

A 15ft × 12ft room = 180 square feet.

Irregular Rooms — Divide and Conquer

For L-shaped rooms or spaces with alcoves, split the area into rectangles. Calculate each section's square footage separately, then add them together for the total.

Circular Areas

Area = π × radius²

Measure the diameter, divide by 2 for radius. A 10-foot diameter circle: radius = 5 ft, area = π × 5² ≈ 78.5 square feet.

Always Add Waste Allowance

Standard recommendation is 10% extra for cuts, mistakes, and pattern matching. For diagonal tile or plank installations, or rooms with many angles, increase to 15%.

Converting to Square Yards

Carpet is often priced per square yard. Divide square feet by 9 (since 1 square yard = 9 square feet). A 180 sq ft room = 20 square yards.

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Frequently Asked Questions

Add 10% to your calculated square footage for standard installations. For diagonal patterns or rooms with many cuts and angles, increase to 15% to avoid running short.
Divide the L-shape into two rectangles, calculate the square footage of each separately, then add the two totals together for the combined area.
Sources: Figures and guidelines cited above are drawn from federal agencies and recognized industry bodies (IRS, Institute of Medicine, ACOG, CDC) current as of 2026. Always verify current-year figures, as thresholds adjust annually.