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How to Calculate Square Feet
Whether you are planning a DIY home improvement project, purchasing hardwood flooring, buying fertilizer for your lawn, or renting a home, knowing how to calculate square footage is an essential life skill. Square footage measures the two-dimensional surface area inside a room or boundary, and calculating it is simple once you have the correct measurements.
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Laying Out the Math: Length × Width
How to Calculate Square Footage in 3 Steps
For any standard rectangular space (like a bedroom, patio, or driveway), you can calculate the square footage by following these simple steps:
- Measure the length and width: Use a tape measure to find the length and width of the space in linear feet. If your measurement includes inches, divide the inches by 12 to convert them to decimals (e.g., 6 inches = 0.5 feet).
- Multiply the length by the width: Multiply the two measurements together.
- Label the result: Write your final answer in square feet (e.g., sq ft, sq. ft., or ft²).
Worked Example:
A living room measures 18 feet 6 inches long and 14 feet wide. Calculate the square footage:
- Convert length to decimal: 18 + (6 ÷ 12) = 18.5 feet
- Multiply dimensions: 18.5 feet × 14 feet
- Perform math: 18.5 × 14 = 259
- Result: 259 square feet
Calculating Area for Irregular or L-Shaped Rooms
Not all rooms are perfect rectangles. If you have an L-shaped room, an alcove, or an entry closet, you can calculate the total square footage by splitting the room into smaller sections:
- Divide the space into sections (e.g., Rectangle A and Rectangle B).
- Measure and multiply the length and width of Rectangle A.
- Measure and multiply the length and width of Rectangle B.
- Add the two areas together to find the grand total.
For circular patios or odd-angled corners, you can use specialized formulas:
- Circle Area: Area = 3.14159 × radius²
- Triangle Area: Area = ½ × base × height
Ordering Materials & The Waste Factor
When purchasing materials like tile, paint, or turf, never buy the exact square footage of your space. Installing materials requires cutting and fitting them into corners, which creates scrap.
Standard guidelines recommend adding a 10% waste factor to your total area. To do this, multiply your square footage by 1.10.
Example: Material Ordering
Total calculated space: 180 sq ft
10% waste buffer: 180 × 0.10 = 18 sq ft
Total material to order: 180 + 18 = 198 sq ft (or 180 × 1.10 = 198 sq ft)
Interactive Construction Estimators
Avoid manual math errors. Use our specific calculators to estimate floor tiles, paints, and square footage:
Square Footage Calculator
Easily compute square footage for multiple rooms, include waste margins, and calculate material costs.
Flooring Calculator
Estimate flooring materials, subfloors, trim, and labor costs for hardwood, laminate, or carpet.
Tile Calculator
Calculate the number of floor or wall tiles needed for any dimensions, with layout patterns and grout lines.
Area Formulas Resource
Reference geometric area formulas for squares, circles, trapezoids, and triangles.
Frequently asked questions
A square foot is a unit of area measurement that represents the space inside a square that is exactly 1 foot long and 1 foot wide. It is commonly abbreviated as sq. ft., sq ft, or ft².
To find the square footage of an irregular room, divide the space into smaller, standard shapes (like rectangles, squares, or triangles). Calculate the area of each shape individually, then add the results together. For example, an L-shaped room can be split into two rectangles.
To convert square inches to square feet, divide the total square inches by 144 (since there are 12 × 12 = 144 square inches in one square foot). To convert square yards to square feet, multiply the square yards by 9 (since 1 yard = 3 feet, so 1 square yard = 3 × 3 = 9 square feet).
It is standard practice to add a 10% waste allowance to your total calculated square footage for tile, hardwood, or laminate flooring projects. This covers cut-offs, mistakes, and diagonal trimming. If you are installing tiles diagonally, increase this allowance to 15%.