How to Calculate Square Footage
To calculate square footage (sq ft), measure the length and width of a space in feet (ft), then multiply the two measurements together. The result is the area in square feet.
Basic Formula for Area
For a room that measures 15 feet (4.57 meters) long and 12 feet (3.66 meters) wide, the area is 180 square feet (16.72 square meters). Measure both dimensions in the same unit before multiplying. Convert inches (in) to feet by dividing by 12, since 1 foot equals 12 inches (30.48 centimeters).
Square Footage Calculator for Odd Shaped Room
To calculate square footage for an odd shaped room, divide the room into smaller regular shapes such as rectangles and triangles. Calculate the area of each shape separately, then add the individual areas together to get the total square footage.
Example Calculation
An L-shaped room has 2 rectangular sections. Section A measures 10 ft × 12 ft = 120 sq ft (11.15 sq m). Section B measures 8 ft × 6 ft = 48 sq ft (4.46 sq m). The total area for the odd shaped room is 120 + 48 = 168 sq ft (15.61 sq m).
Area Formulas for Different Shapes
There are 5 common area formulas used in a square footage calculator. Select a shape below to see the formula, diagram, and example calculation for each shape.
Square
A square shape with sides of 10 feet (3.05 meters) has an area of 100 square feet (9.29 square meters). All 4 sides of a square are equal in length.
Rectangle
A rectangle shape measuring 15 feet (4.57 m) long and 10 feet (3.05 m) wide has a rectangle area of 150 square feet (13.94 square meters). The rectangle area formula is the most commonly used formula in square footage calculations.
Circle
A circle shape with a diameter of 10 feet (3.05 meters) has a radius of 5 feet. The area of a circular shape is π × 5² = 78.54 square feet (7.30 square meters). Use this formula for round rooms, pools, and circular driveways.
Triangle
A triangle shape with a base of 12 feet (3.66 m) and a height of 8 feet (2.44 m) has an area of 48 square feet (4.46 sq m). Use this formula for triangular shapes in gable walls, roof sections, and angled corners.
Trapezoid
A trapezoid with a top base of 8 feet (2.44 m), a bottom base of 14 feet (4.27 m), and a height of 6 feet (1.83 m) has an area of 66 square feet (6.13 sq m). Use the trapezoid formula for cathedral walls, right trapezoid shapes, and sloped ceilings.
How to Figure Out the Square Footage of a Wall
To calculate the square footage of a wall, multiply the wall height by the wall width. Subtract the area of any windows or doors from the total wall area to get the net paintable or coverable surface.
Wall and Window Shape
A wall that measures 10 feet (3.05 m) wide and 8 feet (2.44 m) tall has 80 square feet (7.43 sq m) of total area. A window measuring 3 ft × 4 ft occupies 12 sq ft (1.11 sq m). The net wall area is 80 − 12 = 68 square feet (6.32 sq m). Subtract additional areas for doors, vents, and other openings when calculating square footage for drywall or painting a house.
How to Calculate the Square Footage of a House
To calculate the square footage of a house, measure the length and width of each room, calculate each room's area in square feet, then add all room areas together. The square footage of a house includes all finished, conditioned (heated and cooled) spaces measured from the exterior walls.
Bedrooms, living rooms, kitchens, bathrooms, and hallways count toward the total square footage of a house. Garages, unfinished basements, unfinished attics, and covered porches are excluded from the standard square footage in most real estate listings, excluding non-conditioned spaces from the total.
Usable square footage is the floor area a homeowner or tenant occupies directly. Usable square footage excludes shared areas such as lobbies, stairwells, and mechanical rooms. Usable square footage is always smaller than gross square footage in commercial real estate and multi-story additions.
Calculations for L-Shaped Rooms or Areas
To calculate the area of L-shaped rooms, split the L-shape into 2 separate rectangles. Measure the length and width of each rectangle, calculate each rectangle area, then add both areas together for the total square footage.
There are 4 steps to calculate square footage of L-shaped rooms:
Step 1: Identify where the L-shape divides into 2 rectangles.
Step 2: Measure the length and width of Rectangle A and Rectangle B.
Step 3: Calculate Area A = Length × Width and Area B = Length × Width.
Step 4: Total Area = Area A + Area B.
Total = 200 + 110 = 310 sq ft (28.80 sq m). Click the button above to see the L-shaped room split into 2 rectangles for irregular layouts.
Adding 10% Surplus for Materials
Add a surplus percentage to the calculated square footage before purchasing materials for flooring installation, painting a house, or drywall work. The surplus accounts for cuts, waste, mistakes, and pattern matching during installation. Most contractors recommend adding 10% surplus for standard materials.
Waste Percentages by Material Type
| Material Type | Waste Percentage | Multiply Area By |
|---|---|---|
| Standard Flooring (vinyl, laminate) | 5–10% | × 1.10 |
| Diagonal / Herringbone Pattern | 10–15% | × 1.15 |
| Complex Tile Patterns | 15–20% | × 1.20 |
| Hardwood Flooring | 5–10% | × 1.10 |
| Carpet | 5–10% | × 1.10 |
| Drywall | 10–15% | × 1.15 |
| Painting (coverage) | 5–10% | × 1.10 |
How to Calculate Price Per Sq Ft
To calculate cost per square foot, divide the total cost by the total area in square feet. The price per sq ft formula works for painting a house, flooring installation, and building a home.
Painting a House
One gallon of paint covers 350 to 400 square feet (32.5 to 37.2 square meters) on average. For a house with 2,500 sq ft of wall area and paint priced at $35 per gallon, the paint cost is approximately $219 to $250.
Flooring Installation
For a 1,500 sq ft (139.35 sq m) house with flooring priced at $4 per sq ft and a 10% waste factor, the total flooring cost is 1,500 × $4 × 1.10 = $6,600.
Building a Complete Home
The average cost to build a home ranges from $100 to $200 per square foot, depending on location, materials, and finishes. A 2,000 sq ft (185.81 sq m) home at $150 per sq ft costs $300,000 total.
How to Use the Square Footage Calculator
There are 6 steps to use the square footage calculator on this page.
Select a Shape
Choose from the shape selector: rectangle, circle, triangle, trapezoid, sector, parallelogram, annulus, rectangle border, or circle ring.
Enter Dimensions
Type the length, width, radius, or other measurements for the selected shape into the input fields.
Choose Units
Select the measurement unit: feet (ft), inches (in), meters (m), centimeters (cm), yards (yd), or millimeters (mm).
Calculate Area
Click the "Calculate" button to compute the area in square feet (sq ft) and square meters (sq m).
Add Rooms
Click "Add Room" to save the calculation and start measuring another room. The calculator sums all room areas automatically.
Export Results
Use the "Export" button to download all room calculations as a text file for renovation planning or before flooring purchase.
Basic Length Conversion
Use the table below to convert between common length units when measuring square footage. Convert all dimensions to the same unit before multiplying length by width.
| From | To | Multiply By | Example |
|---|---|---|---|
| Feet (ft) | Inches (in) | × 12 | 10 ft = 120 in |
| Inches (in) | Feet (ft) | ÷ 12 | 36 in = 3 ft |
| Feet (ft) | Meters (m) | × 0.3048 | 10 ft = 3.048 m |
| Meters (m) | Feet (ft) | × 3.2808 | 3 m = 9.84 ft |
| Feet (ft) | Centimeters (cm) | × 30.48 | 5 ft = 152.4 cm |
| Feet (ft) | Yards (yd) | ÷ 3 | 12 ft = 4 yd |
| Yards (yd) | Feet (ft) | × 3 | 5 yd = 15 ft |
| Meters (m) | Centimeters (cm) | × 100 | 2.5 m = 250 cm |
| Inches (in) | Millimeters (mm) | × 25.4 | 6 in = 152.4 mm |
Area Conversion
Use the table below to convert between common area units. These conversions are used during renovation planning, commercial real estate audits, and HVAC sizing for multi-story additions.
| From | To | Multiply By | Example |
|---|---|---|---|
| Square Feet (sq ft) | Square Meters (sq m) | × 0.0929 | 500 sq ft = 46.45 sq m |
| Square Meters (sq m) | Square Feet (sq ft) | × 10.764 | 50 sq m = 538.2 sq ft |
| Square Feet (sq ft) | Square Yards (sq yd) | ÷ 9 | 1,800 sq ft = 200 sq yd |
| Square Feet (sq ft) | Acres | ÷ 43,560 | 43,560 sq ft = 1 acre |
| Acres | Square Feet (sq ft) | × 43,560 | 0.5 acre = 21,780 sq ft |
| Square Inches (sq in) | Square Feet (sq ft) | ÷ 144 | 1,728 sq in = 12 sq ft |
| Square Meters (sq m) | Square Centimeters | × 10,000 | 1 sq m = 10,000 sq cm |
| Acres | Square Meters (sq m) | × 4,046.86 | 1 acre = 4,046.86 sq m |