What is a square foot?
A square foot (sq ft) is a measurement of two-dimensional area. One square foot equals a square that is 1 foot (12 inches) long on each side. It is the standard measurement unit used for assessing property dimensions, room sizes, and estimating material coverage like flooring, paint, and landscaping.
How to Calculate Square Footage
To calculate square footage, measure the length and width of your space in feet and multiply those two numbers together. This calculation provides the total area square footage.
Example Calculation
A room is 12 feet long and 10 feet wide. Multiply 12 by 10 to get 120. There are 120 square feet in the room.
Basic Formula for Area
The basic formula for area is Length × Width. Measure both the length and width in the same unit before multiplying.
Basic Length Conversion
There are 3 main length conversions you need for area measurement:
- Inches to feet: Divide the number of inches by 12.
- Yards to feet: Multiply the number of yards by 3.
- Meters to feet: Multiply the number of meters by 3.28084.
Area Conversion
There are 4 common area conversions used in construction estimation:
- To convert square inches to square feet, divide by 144.
- To convert square yards to square feet, multiply by 9.
- To convert square meters to square feet, multiply by 10.7639.
- To convert acres to square feet, multiply by 43,560.
Use our Area Conversion Calculator tool above to automate these conversions.
Area Formulas for Different Shapes
There are 13 geometric shapes supported by the Square Footage Calculator. Below are the specific formulas for estimating area.
Square Shape
Calculate square footage of a square
Formula: Side Length × Side Length. Measure one side of the square and multiply it by itself.
Rectangle Shape
Calculate square footage of a rectangle
Formula: Length × Width. Measure the long side and the short side, then multiply them.
Rectangle Border Shape
Calculate square footage of a rectangle border
Formula: Total Area (Outer Length × Outer Width) − Inner Area (Inner Length × Inner Width). Calculate the large outer rectangle area, then subtract the smaller inner rectangle area.
Wall and Window Shape
Calculate square footage of a wall minus window
Formula: Wall Area (Wall Height × Wall Width) − Window Area (Window Height × Window Width). This reveals the exact paint or drywall coverage needed.
Cathedral Wall
Calculate square footage of a cathedral wall (right trapezoid)
Formula: ½ × Base Width × (Left Wall Height + Right Wall Height). This calculates sloped ceiling walls.
Circle Shape
Calculate square footage of a circle
Formula: π × Radius². Measure the distance from the center to the edge (radius), square it, and multiply by 3.14159.
Circle Border Shape
Calculate square footage of a circle border
Formula: π × (Outer Radius²) − π × (Inner Radius²). Subtract the inner circle area from the outer circle area.
Annulus Shape
Calculate square footage of an annulus
Formula: π × (Outer Radius² − Inner Radius²). This is the mathematical term for a ring or circle border.
Triangle Shape
Calculate square footage of a triangle
Formula (Heron's): √[s(s-a)(s-b)(s-c)], where 's' is half the perimeter. Measure all 3 sides when you do not know the height.
Triangle Shape (Base & Height)
Calculate square footage of a triangle using base and height
Formula: ½ × Base × Height. Measure the bottom length and the straight vertical height.
Trapezoid Shape
Calculate square footage of a trapezoid
Formula: ½ × (Base A + Base B) × Height. Add the parallel sides, multiply by the straight height, and divide by 2.
Sector
Formula: ½ × Radius² × Angle (in radians). This calculates a specific wedge of a circle.
Parallelogram
Formula: Base × Height. Multiply the bottom length by the vertical height.
Calculations for 'L' Shaped Rooms or Areas
Split an irregular shape or L-shaped room into two distinct rectangular sections. Calculate the square footage of each section separately using Length × Width, then add the two results together.
Example Calculation
Section A is 10 ft by 5 ft (50 sq ft). Section B is 6 ft by 4 ft (24 sq ft). The total is 74 square feet.
Calculating Square Footage for Walls
Measure the wall width and the wall height in feet. Multiply the width by the height. Subtract the area of any doors or windows to find the exact paint coverage required.
Calculating the Square Footage of a House or Property
Measure the length and width of every rectangular room inside the building. Calculate the area for each room, then add the totals together. Exclude unfinished basements and garages from standard real estate square footage.
Adding Surplus for Materials
Construction projects require purchasing 5% to 15% more material than the exact calculated area to account for cutting, mistakes, and material waste factor. Use our material waste toggle in the calculator tool to add this surplus automatically.
Waste Percentages by Material Type
There are 3 standard waste percentages for construction materials:
- Hardwood flooring: Add 5% for standard rooms, 10% for diagonal layouts.
- Tile projects: Add 10% to 15% for complex patterns and breakage.
- Paint: Add 10% for spillage and touch-ups.
Calculating Cost Per Square Foot
Divide the total project cost by the total square footage. For example, a $1,000 project covering 200 sq ft costs $5 per square foot.
Painting a House
Measure the height and width of all exterior walls. Subtract the windows and doors. Multiply the remaining square footage by the paint coverage rate (usually 350 sq ft per gallon).
Flooring Installation
Calculate the floor area square footage and add a 10% waste factor. Multiply this total by the price per square foot of your flooring material.
Building a Home
Multiply the architectural floor plan area by the regional building cost per square foot to estimate total construction costs.
Calculate Cost of Materials
Use the Material Cost toggle in our calculator. Input the price per unit and the currency. The calculator will multiply the final project area (including any waste percentage) by the material cost.
How to Use the Square Footage Calculator
Select your shape from the dropdown menu. Input the length, width, or required dimensions into the fields. Set your desired measurement units. The calculator automatically computes the square footage online.
How to Calculate Square Footage Pricing
Calculate your total area footprint, add your waste factor margin, and multiply the final square footage by the contractor or material rate per square foot.
Calculate square footage (sq ft) from other units
Input your measurements into our tool using yards, meters, or inches. The calculator engine automatically converts these inputs and outputs the result in square feet.
How do I convert square meters to square feet?
Multiply the area in square meters by 10.7639 to get square feet.
How do I convert acres to sq ft?
Multiply the number of acres by 43,560 to get square feet.
Final Remarks About Square Footage
Accurate space estimation and precise layout calculation prevent material shortages and budget overruns. Whenever estimating bulk materials like mulch or gravel, calculate the area first, then calculate Volume to Cubic Yards.