How to Calculate Square Footage

Square footage tells you the area of a flat surface. You need it when buying flooring, painting walls, listing a home for sale, or ordering materials for a construction project. The math is straightforward: measure two sides, multiply them, done.

This guide walks through the formula, shows you how to handle rooms with feet-and-inches measurements, covers irregular shapes like L-shaped rooms, and includes a reference table of common room sizes. If you want to skip the reading and jump straight to a tool, use our square yard calculator or the area calculator.

What Is Square Footage?

A square foot is the area covered by a square that measures 1 foot on each side. That's 12 inches × 12 inches, or 144 square inches.

When someone says a room is "200 square feet," they mean the floor covers the same area as 200 of those 1×1 foot squares laid side by side. The abbreviation is sq ft or ft².

Square footage shows up everywhere:

• Real estate — home listings use it to describe house size
• Flooring — hardwood, tile, and carpet are sold by the square foot (or square yard)
• Paint — a gallon of paint covers about 350–400 sq ft
• Construction — contractors price work per square foot
• Gardening — fertilizer and seed coverage is rated in sq ft

The Square Footage Formula

For any rectangle or square, the formula is:

Measure the length of one wall. Measure the width of the perpendicular wall. Multiply them. Try it right now with our live interactive visual calculator below:

Example: A room is 10 feet long and 12 feet wide. The area is 10 × 12 = 120 square feet.

If your measurements are in different units, convert to feet first:

• Inches to feet: divide by 12
• Yards to feet: multiply by 3
• Meters to feet: multiply by 3.281

How to Measure a Room

Here's the step-by-step process:

1. Get a tape measure. A 25-foot retractable tape works for most rooms. For large spaces, a laser distance measurer is faster and more accurate.
2. Measure the length. Run the tape along the longest wall from one corner to the opposite corner. Write it down.
3. Measure the width. Measure the wall perpendicular to the first one, corner to corner.
4. Multiply. Length × Width = square footage.

Calculating Square Footage from Feet and Inches

Most tape measures show feet and inches together — something like 12 ft 6 in. You can't just multiply "12.6 × 10.3" because those aren't decimal numbers. You need to convert the inches to a decimal fraction of a foot first.

Round to the nearest whole number for most projects: 128 sq ft. If you're buying materials, round up to avoid coming short.

Want a shortcut? Our inches calculator handles the conversion for you — just type your measurements in inches and get square yards instantly.

Square Footage of Common Rooms

Use this table as a quick reference for typical room sizes in a US home:

These are averages. Your rooms may differ. Always measure — don't guess.

Calculating Total House Square Footage

To get the total square footage of a house, measure each room individually and add them up.

Example:

• Living room: 216 sq ft
• Kitchen: 100 sq ft
• Bedroom 1: 120 sq ft
• Bedroom 2: 150 sq ft
• Bathroom: 40 sq ft
• Hallway: 30 sq ft

Total: 656 sq ft

Don't forget hallways, closets, and utility rooms. They count toward total floor area. Garages, unfinished basements, and outdoor patios usually don't count in real estate listings, but they matter if you're buying paint or flooring for those areas.

How to Calculate Square Footage for Irregular Shapes

Not every room is a perfect rectangle. The secret to measuring irregular rooms is simple: break them down into basic shapes (rectangles, triangles, or circles), calculate each area separately, and add them together.

L-Shaped Rooms

Split the room into two rectangles with an imaginary dividing line. Measure each section, multiply its length by its width, and add the two numbers. Try the visual interactive demo below:

For more complex shapes, our shape calculator handles rectangles, triangles, and circles with one click. And for multi-room or odd floor plans, the irregular shape calculator lets you add multiple sections together.

Square Footage to Square Yards

Carpet stores and flooring suppliers frequently price and sell products per square yard, not per square foot. To convert:

Why 9? Because 1 yard = 3 feet, so 1 square yard = 3 × 3 = 9 square feet.

Example: Your room is 180 sq ft. That's 180 ÷ 9 = 20 square yards. If carpet costs $25 per square yard, your total is 20 × $25 = $500.

Use the main calculator to convert between square feet, square yards, square meters, and acres in one step. Or check the carpet calculator for roll width and seam planning.

Common Mistakes to Avoid

1. Confusing linear feet with square feet. A 10-foot board is 10 linear feet. A 10 × 10 room is 100 square feet. These are different measurements. Linear feet measure distance in one direction. Square feet measure area.
2. Forgetting to convert inches. If your room is 12 ft 6 in wide, don't plug in 12.6. Convert the inches: 6 ÷ 12 = 0.5, so the width is 12.5 feet.
3. Measuring only one wall. If the room narrows or has an alcove, the opposite wall may be a different length. Measure both ends and use the average, or split the room into sections.
4. Not adding waste factor. When ordering flooring or tile, add 10% extra for cuts and waste. A 200 sq ft room needs about 220 sq ft of material. For diagonal patterns, add 15%.

Try the Calculator

Skip the manual math. Our square yard calculator takes your length and width in any unit — feet, meters, inches, yards, centimeters — and gives you the area in square yards, square feet, square meters, and acres. Add a cost per unit to get a price estimate.

For material-specific calculations, check out:

• Flooring calculator — plank types, box quantities, and waste factor
• Carpet calculator — roll width, seam layout, and carpet cost
• Concrete calculator — cubic yards and bag count from area × thickness
• Price calculator — cost per sq ft, sq yd, or sq m in any currency