What is square foot?
A square foot is a unit of area in imperial and US customary systems equal to 144 square inches. It is commonly used in the United States for real estate listings, floor plans, and building layouts.
Real-world uses
Square feet are the primary unit for real estate in the United States, Canada, and parts of South Asia. Office space, apartment listings, and retail floor plans are quoted in sq ft. Flooring, tiles, and paint coverage are sold per square foot in these markets.
History
The square foot derives directly from the foot, which has been used since ancient times. It became the de facto real estate standard in the United States and remains deeply entrenched in American property markets despite the global shift toward metric units.
Common mistakes
Forgetting that square footage is an area measure, not a length. A 1,000 sq ft apartment is not 1,000 feet long. Also, nominal tile sizes often include grout spacing, so actual coverage per tile is slightly less than the stated size.
What is square mile?
A square mile is a unit of area in imperial and US customary systems equal to 640 acres. It is used to express the size of cities, regions, and geographic territories in the United States and United Kingdom.
Real-world uses
Square miles are used for city areas, county sizes, and population density calculations in the US and UK. Manhattan is about 23 square miles. National parks and wilderness areas are often described in square miles in American contexts.
History
The square mile became a standard geographic unit in English-speaking countries alongside the statute mile. The US Public Land Survey System, established in 1785, divided territory into 36-square-mile townships, each containing 36 one-square-mile sections.
Common mistakes
Assuming 1 square mile = 1 mile × 1 mile = 1 mi². While correct, people forget that 1 sq mi = 640 acres or about 2.59 km², leading to errors when comparing American and metric area figures.
When is this conversion used?
Converting square foot to square mile is useful in the area domain when comparing values across different measurement standards or applying formulas that require a specific unit.
Worked examples
1 square foot = 3.587006e-08 square mile
1 square mile = 2,589,988.110336 square metre
How to convert square foot to square mile
To convert square foot to square mile, multiply the value by 3.587006e-08.
To convert square mile back to square foot, multiply by 27,878,400.
Measurement standards
The square metre is the SI derived unit of area. The hectare (10,000 m²) is accepted for use with the SI by the BIPM, particularly for land measurement, though it is not an SI unit itself.
Did you know?
Vatican City, the world's smallest independent state, covers just 0.44 km² (about 109 acres) — smaller than many golf courses. By contrast, Russia spans over 17.1 million km², nearly 39 million times larger.
Quick reference: square foot to square mile
| square foot | square mile |
|---|---|
| 0.1 | 3.587006e-09 |
| 0.5 | 1.793503e-08 |
| 1 | 3.587006e-08 |
| 2 | 7.174013e-08 |
| 5 | 1.793503e-07 |
| 10 | 3.587006e-07 |
| 25 | 8.967516e-07 |
| 50 | 0.00000179 |
| 100 | 0.00000359 |
| 250 | 0.00000897 |
| 500 | 0.00001794 |
| 1,000 | 0.00003587 |
Common values
| square foot | square mile | |
|---|---|---|
| A4 paper | 0.66736245 square foot | 2.393833e-08 square mile |
| Parking space | 134.54888021 square foot | 0.00000483 square mile |
| Tennis court | 2,807.98131041 square foot | 0.00010072 square mile |
| Football field (soccer) | 76,854.32037531 square foot | 0.00275677 square mile |
| Central Park, NYC | 36,704,934.52098015 square foot | 1.31660836 square mile |