| Reference | Feet (ft) | Miles (mi) |
|---|---|---|
| A sheet of A4 paper (long side) | 0.974409 ft | 0.000184547 mi |
| Average adult human height | 5.57743 ft | 0.00105633 mi |
| A football pitch (length) | 344.488 ft | 0.065244 mi |
| A marathon | 138435 ft | 26.2188 mi |
| Height of Mount Everest | 29032.2 ft | 5.49851 mi |
The foot is a unit of length equal to exactly 0.3048 metres, or twelve inches. Its plural is feet and its symbol is ft, though a single prime is used in technical drawing and a straight apostrophe informally.
Units based on the human foot appear across the ancient world, and their lengths varied considerably. The Roman pes measured about 296 millimetres and was divided into twelve unciae, an arrangement English inherited directly. Medieval Europe supported dozens of local feet, and a merchant crossing a few borders might encounter several. The English foot was standardised in stages, but its exact modern value dates only from the International Yard and Pound Agreement of 1959.
Aviation is the foot's most significant surviving international domain. Aircraft altitude is reported in feet almost everywhere, and flight levels are expressed in hundreds of feet, so FL350 means 35,000 feet. Russia and China historically used metres, and China's transition to feet for most flight levels in 2011 removed a genuine safety hazard at the boundaries of adjoining airspace. Vertical separation standards are defined in feet, and reduced vertical separation minima allow 1000 feet between aircraft above 29,000 feet.
Construction in the United States works in feet and inches throughout, and lumber, ceiling heights and room dimensions all follow. Broadcasting and film retain the foot for lens focus scales and for measuring film stock. Water depth in diving is given in feet in American practice and metres elsewhere, a divergence that dive computers accommodate by offering both.
Twelve as a divisor is the foot's practical strength. It divides evenly by two, three, four and six, which suits carpentry and layout work where thirds and quarters are common. A decimal unit divides cleanly only by two and five.
Water and timber keep two of its derivatives alive. The fathom, six feet, measured the depth of water for as long as a sounding line was thrown by hand, and old charts are still marked in fathoms even where new ones use metres. The board foot, a volume of one foot square by one inch thick, remains the trading unit of sawn timber in North America, so a lumber yard quotes prices per thousand board feet. Both illustrate a general habit of the imperial system: rather than adding prefixes, it names each new quantity after the job it does, which makes the units memorable to those who use them and opaque to everyone else.
One foot equals 12 inches, 0.3048 metres, or 30.48 centimetres exactly.
The mile is a unit of length equal to 5280 feet, 1760 yards, or exactly 1609.344 metres. The symbol is mi. It is the principal unit of road distance in the United States and the United Kingdom.
Its name comes from the Roman mille passus, a thousand paces, where a pace counted two steps. That unit measured about 1479 metres, appreciably shorter than the modern mile. The English mile grew to its present length because it was reconciled with the furlong, an older agricultural measure. Making the mile eight furlongs required 5280 feet, and Parliament fixed that figure by statute in 1593, which is why the unit is sometimes called the statute mile to distinguish it from other historical miles.
Those alternatives were numerous. The Scots mile, the Irish mile and various German and Scandinavian miles all differed, some substantially. The Swedish mil, still used colloquially, is ten kilometres.
Road signs, speed limits and vehicle odometers use the mile in the United States, the United Kingdom, Liberia and Myanmar, and speeds are given in miles per hour. The United Kingdom's position is inconsistent by design: distances and speeds are imperial while most other official measurement is metric, an arrangement that has survived repeated proposals for change.
Athletics keeps the mile as the one non-metric distance with continuing international standing. World records are ratified over the mile alongside metric distances, largely because of the historical weight of the four-minute barrier broken by Roger Bannister in 1954. The current record stands under 3 minutes 44 seconds.
Fuel economy in the United States is expressed as miles per gallon, and aviation and shipping use the separate nautical mile, which is longer at 1852 metres and unrelated in derivation.
The map of the United States is drawn on it. The Public Land Survey, begun in 1785, divided the western territories into townships six miles square, each containing thirty-six sections of one square mile, and each section of 640 acres subdividing neatly into quarters and quarter-quarters. Roads followed the section lines, which is why so much of the American Midwest is a grid of straight routes one mile apart, and why farms there are described in quarter sections rather than in acres. Anyone flying over Iowa or Kansas is looking at the mile drawn across an entire landscape, two centuries after the surveyors laid it out.
One mile equals 1760 yards, 5280 feet, 8 furlongs, or 1609.344 metres. A five-kilometre race is about 3.107 miles.