How to Calculate Square Footage of a Room
Published 2026-02-01 · Updated 2026-07-14
Square footage tells you how much floor area a room has. It is used for paint planning, flooring, rugs, cleaning estimates, furniture layouts, rent comparisons, and home improvement projects.
Basic square footage formula
For a rectangular room, use this formula: square footage = length x width.
Measure both sides in feet. If your tape measure gives inches, convert inches to decimals or divide inches by 12 before multiplying.
Example room measurement
A room that is 12 feet long and 10 feet wide has 120 square feet of floor area. A room that is 15 feet by 11.5 feet has 172.5 square feet.
For flooring, it is common to add extra material for waste, cuts, and mistakes. The extra amount depends on the material and room shape.
How to handle irregular rooms
For L-shaped or irregular rooms, split the space into smaller rectangles. Calculate each rectangle separately, then add the areas together.
Do not subtract closets or alcoves unless the project specifically excludes them. For most flooring and cleaning estimates, those areas still count.
Quick Summary
Measure length and width in feet, multiply them, and add separate rectangles together for irregular rooms.