Square Footage Calculator

The Formula

Square footage measures the area of a space in square feet. Different shapes use different area formulas. For rectangles multiply length by width. For circles use π times the radius squared. For L-shaped rooms divide into two rectangles and add their areas.

Variable Definitions

How to Use This Calculator

1. 1

   Select the shape of the area: rectangle, circle, or L-shape.

2. 2

   Enter the required dimensions for the chosen shape.

3. 3

   Choose your input unit (feet or meters).

4. 4

   Optionally add a waste factor (10% is standard for flooring) and a price per square foot for a cost estimate.

Square footage is calculated by dividing irregular spaces into rectangles, calculating each area, and summing them.

Understanding the Concept

Square footage is the standard unit of area measurement in US real estate and construction. It determines property values, flooring material quantities, paint coverage, HVAC sizing, and more. For simple rectangular rooms, just multiply length by width. For irregular shapes, break the space into rectangles, calculate each area, and sum them. Always add a waste factor (typically 5-15%) when ordering materials like flooring or tile to account for cuts, mistakes, and off-cuts. Practical example: an L-shaped room consists of a 12×10 ft section joined to a 6×8 ft section. Total area = (12 × 10) + (6 × 8) = 120 + 48 = 168 sq ft. For hardwood flooring with a 10% waste factor, order 168 × 1.10 = 184.8 (round to 185 sq ft). At $5.00 per sq ft, estimated cost = $925. In square meters, the area is 168 / 10.764 = 15.6 m². Edge cases: for rooms with triangular sections (e.g., a bay window alcove), use the formula A = ½ × base × height for each triangular section and add it to the rectangular area. For circular rooms or areas (rare in residential but common in some commercial buildings), use A = πr². For rooms measured in meters, the calculator converts to square feet using the factor 1 m² = 10.7639 ft² automatically. For carpet measurement, remember that carpet comes in 12-ft wide rolls, so a room that is 14×10 ft might require 14 ft of 12-ft-wide carpet covering only 10 ft of width, with 2 ft of waste — a different calculation than simple square footage. For paint estimation, one gallon typically covers about 350-400 sq ft of wall area (not floor area), so you need the wall perimeter × ceiling height for the wall surface area. For property listings, note that different US regions measure square footage differently — some include garages and basements, while others count only finished above-grade living space. Always verify which standard is being used when comparing property values.

Frequently Asked Questions

Sources & References