Square Footage Calculator
Measure room area in square feet or meters, handle irregular shapes, and plan flooring, paint, or renovation materials.
Square Footage Calculator
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Understanding Square Footage
Square footage is a measurement of area expressed in square feet. It's essential for home improvement projects, real estate valuations, flooring installations, and space planning. Accurately calculating square footage helps you purchase the right amount of materials, estimate costs, and avoid expensive mistakes.
To calculate square footage, you multiply length by width for rectangular spaces. For irregular shapes like circles or triangles, specific formulas apply. Many real-world spaces are irregular, so breaking them into simpler shapes and adding the areas together provides accurate totals.
This calculator handles rectangles, circles, triangles, and custom multi-room configurations. It also converts between units (feet, inches, meters, centimeters) and provides material estimates with waste factors for practical project planning.
Square Footage Calculation Formulas
Different room shapes require different formulas. Here are the most common calculations for residential and commercial spaces:
Rectangle/Square:
Area = Length × Width
Circle:
Area = π × Radius² (π ≈ 3.14159)
Triangle:
Area = (Base × Height) ÷ 2
Example:
Room: 12 feet × 10 feet (rectangular)
Area = 12 ft × 10 ft = 120 square feet
In square meters = 120 × 0.0929 = 11.15 m²
Total area: 120 sq ft (11.15 m²)
Square Footage Unit Conversions
Understanding unit conversions is crucial when working with different measurement systems or comparing international property sizes:
Pro Tip: When converting measurements, square the conversion factor. For example, since 1 ft = 12 inches, then 1 sq ft = 12² = 144 sq inches.
Material Estimation Guidelines
Flooring (10% Waste)
Add 10% to account for cutting waste, pattern matching, and future repairs. For diagonal installations, add 15%. Always round up to full boxes or cartons.
Paint Coverage
One gallon covers ~350 sq ft per coat. Multiply total square footage by 2 for two coats, then divide by 350. Rough or porous surfaces require 20-30% more paint.
Carpet (5% Waste)
Carpet is sold by square yard. Divide sq ft by 9 to get sq yards, then add 5% waste. Hallways and stairs require special calculations and professional measurement.
Tile (15% Waste)
Tile projects need 15% waste for cuts, breakage, and future repairs. Complex patterns or diagonal layouts may require 20% waste. Order extra for repairs as exact matches become unavailable.
Measurement Best Practices
Measure Twice, Calculate Once
Always measure each dimension at least twice, preferably from different starting points. Use a quality tape measure and have someone help hold it straight for long distances. Even small measurement errors compound when calculating areas.
Break Irregular Rooms into Sections
For L-shaped or irregular rooms, divide the space into rectangles, measure each section separately, then add them together. This is more accurate than trying to measure irregular shapes as a whole. Sketch your floor plan for reference.
Account for Architectural Features
Decide whether to include or exclude closets, alcoves, and built-ins based on your project. For flooring, include closets. For real estate, different markets have different standards - some include closets in room square footage, others don't.
Use Consistent Units
Measure everything in the same units (all feet or all meters) before calculating. If you measure one dimension in feet and another in inches, convert before multiplying. Our calculator handles mixed units automatically.
Frequently Asked Questions
How do I measure a room for square footage?
For rectangular rooms, measure the length and width in feet using a tape measure, then multiply them together. For example, a 12 ft × 10 ft room = 120 square feet. For irregular rooms, break the space into rectangles, calculate each section separately, then add them together. Always measure at the widest points and include closets if calculating for flooring.
What is the difference between square feet and square yards?
Square feet and square yards measure area but use different scales. One square yard equals 9 square feet (3 feet × 3 feet). Carpet is typically sold in square yards while most other materials use square feet. To convert, divide square feet by 9 to get square yards, or multiply square yards by 9 to get square feet.
How much extra material should I order for waste?
Add 10% for standard flooring installations, 15% for tile or diagonal patterns, and 5% for carpet. This accounts for cutting waste, pattern matching, mistakes, and future repairs. For complex room shapes or intricate patterns, consider adding 20%. Always round up to full boxes or rolls as you cannot purchase partial quantities.
How do I calculate square footage for an L-shaped room?
Divide the L-shape into two rectangles. Measure each rectangle's length and width separately, calculate the area of each (length × width), then add the two areas together. For example, if one section is 10×12 (120 sq ft) and the other is 8×6 (48 sq ft), the total is 168 sq ft.
Do I include closets when measuring room square footage?
It depends on your purpose. For flooring projects, include closets since you'll install flooring there. For real estate listings, standards vary by region - some markets include closets in bedroom square footage, others don't. For heating/cooling calculations, include all enclosed spaces. When in doubt, measure and note closets separately.
How many square feet does a gallon of paint cover?
One gallon of paint typically covers 350-400 square feet per coat on smooth surfaces. For rough, textured, or porous surfaces, estimate 250-300 sq ft per gallon. Most projects need two coats, so divide your total square footage by 350, then multiply by 2 to determine gallons needed. Round up to whole gallons.
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