Square Foot Calculator
Calculate the area of any space in seconds. Enter your dimensions below for an instant, accurate square footage result.
Calculate Square Footage
All Square Foot Calculators
Choose a specialized calculator for your specific project type.
Square Foot Calculator Formula
A square foot calculator uses the formula area = length × width to compute the square footage of a space. This formula applies to rectangular and square shapes measured in feet (ft). The result is expressed in square feet (sq ft or ft²), which represents the total area of a flat, two-dimensional surface.
To calculate square footage for different shapes, the square foot calculator applies shape-specific formulas. A rectangle uses length × width. A circle uses π × radius². A triangle uses ½ × base × height. Each formula converts measured dimensions into square feet, square meters (m²), square yards (yd²), square inches (in²), and acres.
How to Calculate Square Foot
To calculate square foot, measure the length and width of the space in feet and multiply the two values together.
Basic Formula for Area
Area is the amount of space occupied by a two-dimensional surface. The surface can be a floor, a wall, a playground, or a field.
The basic formula for area of a rectangle or square is:
An L-shaped or irregular floor plan requires splitting the space into 2 or more rectangles. Calculate each rectangle area separately, then add the results together for the total square footage.
Measure length and width in the same unit. Convert all measurements to feet before multiplying, if your measurements are in different units like inches and feet.
Basic Length Conversion
Convert other units of measure to feet with these formulas:
- Divide inches by 12 to get feet
- Multiply meters by 3.28084 to get feet
- Divide centimeters by 30.48 to get feet
- Multiply yards by 3 to get feet
Area Conversion
Measure your space in any unit, calculate the area, then convert the result to the unit you need. Measure in inches or centimeters, calculate area in square inches or square centimeters, then convert the final answer to square feet or square meters.
| Unit | Equals |
|---|---|
| 1 acre | 43,560 square foot |
| 1 square yard | 9 square foot |
| 1 square meter | 10.76 square foot |
| 1 square inch | 0.00064516 square foot |
| 1 square foot | 0.0929 square meter |
| 1 square foot | 144 square inch |
Area Formulas for Different Shapes
Square Shape
The formula to calculate the area of a square is side length × side length. A square with 8-foot (2.44 m) sides has an area of 64 square feet (5.95 square meters).
Rectangle Shape
A rectangle measuring 15 feet (4.57 m) long and 10 feet (3.05 m) wide has an area of 150 square feet (13.94 square meters). The rectangle area formula is the most common square footage calculation for rooms, lots, and construction projects.
Rectangle Border Shape
Total Area (ft²) = (Length + 2 × Border Width) × (Width + 2 × Border Width)
Area (ft²) = Total Area − Inner Area
Use the rectangle border formula for bordered surfaces, including picture frames, garden borders, and walkway edges. A rectangular garden bed 10 feet by 6 feet with a 2-foot wide border has a border area of (14 × 10) − (10 × 6) = 140 − 60 = 80 square feet.
Circle Shape
This formula uses diameter, the full width across the circle. A circular patio with a 10-foot (3.05 m) diameter has an area of 3.14159 × 5² = 78.54 square feet (7.30 square meters).
Divide the diameter by 2 to get the radius: diameter = 2 × radius. For hand calculations, use π = 3.14159265359 for higher accuracy on larger circle-shaped areas. This square foot calculator uses a high-precision pi constant in circle area calculations.
Circle Border Shape (Ring)
Outer Area (ft²) = π × (Outer Diameter ÷ 2)²
Inner Area (ft²) = π × (Inner Diameter ÷ 2)²
Area (ft²) = Outer Area − Inner Area
Use the circle border formula for ring-shaped surfaces, including circular walkways and decorative borders around round patios.
Annulus Shape
Inner Area (ft²) = π × (Inner Diameter ÷ 2)²
Area (ft²) = Outer Area − Inner Area
The Circle Border and Annulus are the same shape. Circle border area is calculated with border width, and annulus area is calculated with outer diameter.
Triangle Shape
Triangle with Edge Lengths
This is Heron's formula. The sides of the triangle do not need to be equal length. This formula works for any triangle shape, including equilateral, isosceles, and scalene triangles.
Triangle with Base & Height
A triangular area with a base of 8 feet (2.44 m) and a height of 6 feet (1.83 m) has an area of ½ × 8 × 6 = 24 square feet (2.23 square meters).
Trapezoid Shape
The values a and b are the two parallel sides and h is the perpendicular height between the parallel sides. A trapezoid with parallel sides of 12 feet (3.66 m) and 8 feet (2.44 m) and a height of 5 feet (1.52 m) has an area of [(12 + 8) ÷ 2] × 5 = 50 square feet (4.65 square meters).
Sector Shape
A sector is a portion of a circle defined by two radii and an arc. A sector with a radius of 6 feet (1.83 m) and a central angle of 90 degrees has an area of (90 ÷ 360) × 3.14159 × 36 = 28.27 square feet (2.63 square meters).
Parallelogram Shape
A parallelogram with a base of 10 feet (3.05 m) and a height of 7 feet (2.13 m) has an area of 70 square feet (6.50 square meters). The height is the perpendicular distance between the two parallel base sides, not the slanted side length.
Wall and Window Shape
Window Area (ft²) = Window Height × Width
Area (ft²) = Wall Area − Window Area
Use this formula when painting a house or installing siding. Subtract the area of windows and doors from the total wall area to get the paintable surface. Subtract multiple windows of the same size by multiplying window width by the number of windows. Enter the total as the window width. Height remains the height of one window.
The Wall and Window shape also works for a wall with one or more doors or other openings. Enter door dimensions in the Window Width and Window Height fields.
Cathedral Wall (Right Trapezoid)
This calculation covers a wall with a sloped top edge, typical of rooms with cathedral ceilings. The geometric shape is a right trapezoid. An alternate method: break the cathedral wall into a rectangle and a triangle, then add the two areas together.
Calculating Cost Per Square Foot
Painting a house, installing flooring, and building a home all use the square footage of the property to determine cost and material quantities.
Painting a house
Professional house painters base price quotations on the square footage of a property. Measuring square footage yields accurate estimates of the amount of paint required, even for homeowners painting the house themselves.
Total cost encompasses more factors than the amount of paint required, including the cost of materials such as brushes, turpentine, and any materials necessary for preparing, mixing, applying, and cleaning up paint. These considerations are included in a quote from a professional painter, in addition to labor costs. The larger the square footage of a property or area, the higher the cost required to paint the property.
Paint primer helps paint adhere more effectively to surfaces, including wood, metal, plastic, and other materials. Primer generally covers less area than paint. Estimated coverage amounts range from 200 to 400 square feet (18.58 to 37.16 square meters) per gallon (3.79 liters), depending on the method of application, type, and brand of paint.
Flooring installation
There are 3 main categories of flooring materials commonly used for flooring installation: wood, laminate, and tile. Flooring costs vary depending on the quality and choice of materials.
Wood Flooring
Wood flooring includes hardwood, engineered wood (composite or man-made wood), and bamboo. Bamboo is classified as grass, but bamboo is sold and installed as a wood flooring product.
Hardwood flooring is durable, easy to clean, and available in a variety of appearances. Hardwood flooring is versatile for interior design and requires maintenance such as sanding and refinishing over time.
Engineered wood flooring is made from several layers of wood, with a thin outermost layer of the desired hardwood and inner layers such as plywood and high-density fiberboard. Engineered wood has higher heat and moisture resistance than solid hardwood, is easy to maintain, and costs less to purchase and install than hardwood flooring.
Bamboo flooring is moisture resistant, easy to install, and available in many styles. Bamboo flooring costs less than traditional hardwood options. Bamboo does scratch easily from furniture, high heels, claws, and debris.
Laminate Flooring
Laminate flooring is made with plywood or fiberboard and a plastic laminate top layer. Laminate flooring has a similar appearance to hardwood. Laminate flooring costs less than traditional wood flooring, is durable, difficult to scratch, stain, or dent, and requires minimal maintenance. Laminate flooring can be installed over existing flooring, saving time and the cost of removing old flooring. Laminate flooring cannot be refinished or stained, and laminate flooring results in a lower resale value for a home than traditional hardwood.
Tile flooring
Tile flooring includes concrete, cement, ceramic tiles, glass tiles, and natural stone products. Tile prices range from $0.60 per square foot to hundreds of dollars per square foot, depending on the material and quality. Tile is easy to maintain, clean, and suitable for all locations. Tile can be cold in winter without heating, does not dampen sound, can be slippery when wet, and breaks if heavy objects are dropped on the surface. Tile installation is difficult, and installation costs can exceed the cost of the materials.
Building a home
Building plans and visiting different homes help a person gain a better understanding of what square footage works for their preferences during home renovation or new construction.
The cost of building a home varies based on materials, the type of foundation, the pitch of the roof, and many characteristics not directly related to the size of the house. Cost per square foot for building a home is estimated based on averages. Get an estimate from a builder based on specific project specifications, then divide that estimate by the number of square feet the house will occupy.
The cost per square foot of a specific project allows comparison to a different house of similar size as a reference. Houses of the same square footage vary in building cost. Outside costs include fees to local authorities, labor, building code requirements, and insurance.
Frequently Asked Questions
A square foot calculator is an online tool that computes the area of a space in square feet (ft²). Enter length and width measurements, and the calculator multiplies the values to return the total square footage. This calculator supports rectangles, circles, and triangles, and converts results to square meters, square yards, square inches, and acres.
Multiply the length by the width of the space, with both measurements in feet. A room 12 feet long and 10 feet wide has an area of 120 square feet (12 × 10 = 120 sq ft). For circles, use π × radius². For triangles, use ½ × base × height.
Convert inches to feet by dividing by 12, then multiply length by width. A room 10 feet 6 inches long is 10.5 feet (6 ÷ 12 = 0.5). Multiply 10.5 × 8 = 84 square feet. Use the Feet & Inches calculator for separate feet and inches input fields.
The formula is area = length × width. Measure the length and width of the space in feet, then multiply the two numbers. A space 15 feet long and 10 feet wide equals 150 square feet (15 × 10 = 150 sq ft).
Yes, split the irregular shape into simple shapes such as rectangles, triangles, and circles. Calculate the area of each shape separately, then add all the areas together for the total square footage. The Odd Shapes calculator automates this process.
Measure the length and width of each room in feet and multiply to get the area. Add 10% to 15% extra for waste from cuts, mistakes, and future repairs. The Flooring calculator includes a built-in waste factor for hardwood, laminate, vinyl, and carpet.
Multiply the wall height by the wall width to get total wall area, then subtract the area of windows and doors. A wall 10 feet wide and 8 feet tall is 80 square feet. Subtract a 3 × 5 foot window (15 sq ft) to get 65 square feet of paintable surface. Use the Wall calculator to handle multiple walls and deductions.