Square Foot (ft²) - Unit Information & Conversion

Definition

The square foot (plural: square feet; symbol: ft², sq ft, or SF) is an imperial and US customary unit of area. It is defined as the area of a square with sides measuring exactly one foot (0.3048 meters) in length.

One square foot is equal to:

• 144 square inches (in²)
• 1/9 of a square yard (yd²)
• 0.09290304 square meters (m²) (exactly, based on the international foot definition)
• 929.0304 square centimeters (cm²)

It is widely used for measuring room dimensions, house sizes, and smaller land areas in countries using the imperial or US customary systems.

History

• Roots in the Foot: The square foot naturally derives from the foot, a unit of length used since antiquity. The length of the foot varied significantly across different cultures and historical periods, often based on anatomical averages or royal decrees.
• English Standardization: In England, the foot (and thus the square foot) underwent various standardizations. Its use became deeply ingrained in land surveying, architecture, and trade.
• International Foot (1959): To resolve slight discrepancies between the US customary foot and the imperial foot, the "international yard and pound agreement" of 1959 defined the international yard as exactly 0.9144 meters. This implicitly defined the international foot as exactly 0.3048 meters. Consequently, the international square foot is exactly 0.09290304 square meters.
• Persistence: Despite widespread global metrication, the square foot remains the standard unit for many applications, particularly in real estate and construction, in the United States, Canada, the United Kingdom, India, Pakistan, Bangladesh, Malaysia, Singapore, Hong Kong, and several other nations influenced by British or American standards.

Common Uses

The square foot is a ubiquitous unit of area in specific sectors and regions:

• Real Estate (US, Canada, UK, etc.): The primary unit for specifying the area of residential homes, apartments, office spaces, and commercial properties in listings, appraisals, and architectural drawings.
• Construction & Architecture: Used universally in these regions for floor plans, material estimation (flooring, drywall, roofing), and building design.
• Home Improvement: Standard measurement for purchasing materials like tiles, carpet, paint coverage, and wallpaper.
• HVAC Calculations: Used to determine heating and cooling requirements based on room or building area.
• Gardening & Landscaping: Measuring smaller plots, garden beds, patios, or deck areas.
• Rental Space: Often used for pricing storage units or exhibition spaces.
• Art & Signage: Describing the area of canvases, prints, or signs.

Unit FAQs

How big is a square foot visually?

One square foot is the area of a square measuring 1 foot (12 inches or 30.48 cm) on each side. For comparison:

• It's the typical size of a large ceramic floor tile (12"x12").
• It's slightly larger than a standard sheet of US letter paper (8.5"x11" = 93.5 in²).
• A large hardcover notebook might be close to this area.

How many square inches (in²) are in a square foot (ft²)?

There are exactly 144 square inches (in²) in one square foot (ft²). This is because 1 foot = 12 inches, so 1 ft² = (12 inches) × (12 inches) = 144 in².

How many square feet (ft²) are in a square yard (yd²)?

There are exactly 9 square feet (ft²) in one square yard (yd²). This is because 1 yard = 3 feet, so 1 yd² = (3 feet) × (3 feet) = 9 ft².

How do you convert square feet (ft²) to square meters (m²)?

To convert square feet to square meters, multiply the area in square feet by 0.09290304. For a quick approximation, you can divide the number of square feet by 10.764. For example, 100 ft² is exactly 9.290304 m².

How many square feet (ft²) are in an acre (ac)?

There are exactly 43,560 square feet (ft²) in one acre (ac).

Is the square foot (ft²) an SI unit?

No, the square foot is not part of the International System of Units (SI). It is a unit within the imperial system and US customary units. The corresponding SI unit for area is the square meter (m²).