Square Footage Calculator
Area for rooms, floors, walls, and DIY projects
How to Calculate Square Footage
Square footage is how much floor (or wall) area you have in flat units: length times width for a rectangle, or sums of simple shapes for odd rooms. You use it for paint coverage, flooring cartons, carpet sold by the square yard, tile counts, and comparing homes. This calculator keeps everything in one place: several room shapes, multiple rooms, a custom mix of sections, and a material helper with typical coverage rules you can adjust. Use the Square Footage Calculator to get a clear result you can act on right away. This calculator is designed to be practical, fast, and easy to use on any device.
How to measure square footage
Use a tape measure, notepad, and sketch. For each rectangular section, measure the longest straight walls for length and width.
Round to the nearest inch when recording, then let the calculator combine feet and inches. For closets or bump-outs, either include them as part of the rectangle or measure them as a second rectangle and add.
Common mistakes: treating inches as tenths of a foot (10 inches is not 0.10 ft), mixing yards with feet without converting, and using wall height when you only need floor area.
- Measure at the widest points if material will cover the full span.
- For carpet rolls, you may need extra length for seams and direction - ask your installer.
- Building records and listings sometimes measure differently; always verify for purchases.
189.88 sq ft
Unit conversions
- 189.88 square feet (sq ft)
- 21.1 square yards (sq yd)
- 17.64 square meters (sq m)
- 176,399.65 square centimeters (sq cm)
- 27,342 square inches (sq in)
Calculation
Area = length × width = 15.5 ft × 12.25 ft
When you need square footage
Home improvement: paint, flooring, laminate, vinyl, carpet, tile, wallpaper. Real estate: comparing listings and room sizes. Construction and DIY: quick material checks before you quote or buy.
Area unit conversions (reference)
1 sq ft = 144 sq in = 1/9 sq yd ≈ 0.0929 sq m
1 sq yd = 9 sq ft
1 sq m ≈ 10.764 sq ft
1 acre = 43,560 sq ft
Typical room sizes (rough guides): small bedroom ~100 sq ft, average bedroom ~200 sq ft, living room often ~300-500 sq ft. Whole-home sizes vary widely by region and era.
The Formula
How to Calculate Manually
- 1
Pick the shape that best matches your space (rectangle is the default).
- 2
Choose how you want to enter dimensions: feet and inches, decimal feet, meters, centimeters, or yards.
- 3
Enter measurements; results update as you type. Inches roll into feet automatically in the math.
- 4
For L-shaped rooms, either add two rectangles or subtract a cutout from a larger rectangle.
- 5
Use Multiple rooms for a floor total, or Custom to combine rectangles, triangles, and circles.
- 6
Open Material estimator for paint, flooring, carpet, tile, or wallpaper rough quantities.
Examples
12 ft by 14 ft bedroom?
168 sq ft (18.67 sq yd, about 15.6 sq m).
Round room 10 ft across?
Diameter 10 ft → about 78.54 sq ft.
L-shape as 20×15 and 10×8?
300 + 80 = 380 sq ft.
FAQ
How do I measure square footage of a room?
For a rectangle, measure length and width in feet (or feet and inches), then multiply. For odd shapes, split the room into rectangles and triangles, compute each area, and add them.
How many square feet in a square yard?
One square yard is 9 square feet. Divide square feet by 9 to get square yards.
What is the difference between square feet and square meters?
They are different area units. 1 sq m ≈ 10.764 sq ft. This calculator converts both ways from your measured area.
How much paint do I need?
Multiply wall area by the number of coats, then divide by coverage per gallon (often 300-400 sq ft per gallon). Round up and buy an extra quart for touch-ups.
💡 Tips
- •Measure at the longest usable spans if you are buying full flooring or carpet.
- •For paint, walls are not the same as floors: use wall height × perimeter for wall paint, not floor area.
- •Add 5-10% waste for flooring and tile; patterned tile often needs more.
- •Carpet is often priced by the square yard: divide square feet by 9.
- •Odd rooms: split into rectangles and triangles; small errors add up, so remeasure corners.
🎉 Fun Facts
- •One square foot is exactly 144 square inches (12 in × 12 in), which is why tile counts often line up neatly for foot-wide modules.
- •A square yard is 9 square feet, so carpet and broadloom quotes in "yards" are really counting 3 ft × 3 ft chunks of floor.
- •The acre (43,560 sq ft) was historically defined so a one-acre plot could be one furlong long and four rods wide.
- •Gross living area on listings often follows measurement standards (for example ANSI in the U.S.) that define which finished areas count.
- •Doubling each side of a rectangle multiplies area by four, not two - a 10×10 room is 100 sq ft, but 20×20 is 400 sq ft.