Square Footage Calculator Calculators

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Square footage is the area of a space measured in square feet — the standard unit for room size, flooring, real estate listings, and construction projects in the United States. Calculating square footage accurately is essential whether you're buying flooring, estimating paint, planning a garden, or quoting a construction project. The calculation depends on the shape of the space: rectangles and squares are straightforward, but L-shaped rooms, triangles, and circles require different formulas. This guide covers every common shape with clear formulas and worked examples.

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What Is Square Footage?

Square footage is a measure of area in the US customary system, expressed in square feet (ft²). One square foot equals a square with sides of 1 foot (30.48 cm). Area measurements in square feet are used for room size, property size, flooring, landscaping, roofing, and material estimates.

Square Footage Formulas by Shape

Rectangle or Square

Area = Length × Width

A room 12 ft × 15 ft = 180 sq ft

Triangle

Area = ½ × Base × Height

A triangular garden with base 20 ft and height 10 ft = ½ × 20 × 10 = 100 sq ft

Circle

Area = π × r² (r = radius)

A circular patio with diameter 14 ft → radius = 7 ft → Area = π × 7² = 153.9 sq ft

Trapezoid

Area = ½ × (a + b) × h (a and b are parallel sides, h is height)

L-Shaped Room

Divide into two rectangles, calculate each area separately, then add:

Rectangle 1: 10 × 12 = 120 sq ft
Rectangle 2: 8 × 6 = 48 sq ft
Total: 168 sq ft

Converting Units

  • 1 square yard = 9 square feet
  • 1 square meter = 10.764 square feet
  • 1 acre = 43,560 square feet
  • 1 square foot = 144 square inches

Practical Tips

  • Always measure at the longest points of a room — include alcoves and closets
  • For flooring, add 10% waste factor for cuts and mistakes (15% for diagonal patterns)
  • For paint: one gallon covers approximately 350–400 sq ft per coat on smooth surfaces
  • For tile: measure the total area and divide by individual tile size to get the number needed

Glossary

Square Foot (ft²)
A unit of area equal to the area of a square with sides of one foot (30.48 cm). The standard unit for measuring room size, property area, and material quantities in the United States.
Waste Factor
An additional percentage added to a calculated area estimate to account for material waste from cuts, damaged pieces, and pattern matching. Typically 10% for straight flooring, 15% for diagonal patterns.
Square Meter (m²)
The SI unit of area, equal to the area of a square with sides of one meter. Equivalent to 10.764 square feet. Standard for area measurement outside the United States.

Frequently Asked Questions

For a rectangular room, multiply length by width: Area = Length × Width. Measure in feet to get square feet directly. For irregular rooms, divide the space into rectangles, calculate each separately, and sum the areas. Always measure at the longest and widest points, and include built-in closets if calculating for flooring.

One square meter equals 10.764 square feet. To convert square meters to square feet, multiply by 10.764. To convert square feet to square meters, multiply by 0.0929. For example, a 25 m² apartment = 25 × 10.764 = 269.1 sq ft.

Add a 10% waste factor for standard straight-lay flooring to account for cuts, waste, and future repairs. For diagonal or herringbone patterns, add 15%. For irregularly shaped rooms, add 15–20%. It's always better to have a few extra pieces than to run short and need to reorder — dye lots vary and exact matches may not be available later.

Divide the L-shape into two rectangles by drawing a line across the indentation. Measure and calculate the area of each rectangle separately (length × width), then add the two areas together. Alternatively, calculate the area of the full bounding rectangle and subtract the missing corner: Full rectangle − missing corner = L-shaped area.