How do you calculate square footage of a room?

Measuring a room for flooring, paint, or a rental listing starts with one number: square footage. Multiply length by width, both in feet, to find area in square feet.

For a rectangular bedroom 12 feet long and 10 feet wide, calculate 12 × 10 = 120 square feet. That covers the floor only; walls and ceilings use different measurements.

Odd-shaped rooms

Split an odd-shaped space into rectangles or squares you can measure cleanly. Calculate each piece, then add the results. A closet can be excluded or listed separately depending on your purpose.

For a gentle taper, measure the longest and shortest runs and use an average. For triangles, use (base × height) ÷ 2. Reduce curved areas to a trusted formula or make a practical approximation.

Check your units

Measure in the same unit. Twelve inches equal one foot, so 126 inches is 10.5 feet. Mixed units are a common cause of DIY errors.

Doorways and built-ins usually stay inside the floor total unless a contractor requests net usable area. Carpet and tile companies often add 5–10% for cuts and pattern matching. Sketch each section, total the areas, and round up slightly when shopping.

For a quick check, use squarefootagecalculator.org with the same length and width measurements.