Feet to Centimeters (ft to cm)

One international foot equals exactly 0.3048 metre by the International Yard and Pound Agreement of 1959. The foot is divided into 12 inches; three feet make one yard, and 5,280 feet make one statute mile. The standard textual symbol is "ft"; in technical drawings, architectural plans and surveying notation the prime symbol ′ (Unicode U+2032) is used for the foot and the double prime ″ (U+2033) for the inch, so a height of six feet two inches is correctly written 6′ 2″. The earlier US Survey Foot, defined by the 1893 Mendenhall Order as 1200/3937 metre (approximately 0.304800609 m) and retained for geodetic and state-plane work long after 1959, was jointly deprecated by NIST and NOAA's National Geodetic Survey effective 1 January 2023. The foot is recognised by NIST for customary use under Federal Register notice 24 FR 5445, the same instrument that recognises the avoirdupois pound.

The English foot belongs to a family of body-derived length units that descend, by way of the Roman pes, from the Greek pous: the Olympic foot used in stadium-track measurement was about 316 mm and the shorter Attic foot about 308 mm, both rooted in the practical idea that a useful unit of length should be roughly the length of an adult man's foot. The Roman pes, around 296 mm, was divided into sixteen digiti or twelve unciae — and that twelve-part division is the direct ancestor of the twelve-inch foot we use today. Medieval Europe again produced regional variants: the Belgic or "northern" foot at roughly 333 mm, the rather shorter North German foot at about 285 mm, and a clutch of English county and trade feet that varied measurably from one market town to the next. Standardisation in England was a long, statutory affair. Edward I's Compositio Ulnarum et Perticarum, around 1303, fixed three feet to one yard, and Elizabeth I's statute of 1593 set the statute mile at 5,280 feet — eight furlongs of 660 feet apiece. The Imperial Weights and Measures Act of 1824 consolidated those statutes around a brass yard standard kept at Westminster, which was destroyed alongside the pound and yard standards in the 1834 Palace of Westminster fire. The defining moment of the modern foot, however, was the International Yard and Pound Agreement, signed on 1 July 1959 by the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa: it set the international foot at exactly 0.3048 metre and so closed a small but persistent transatlantic gap between the American and Commonwealth definitions. The American foot had been defined since the 1893 Mendenhall Order as 1200/3937 metre — about 0.30480061 m — and that older value, renamed the US Survey Foot, was retained for geodetic surveying and state-plane coordinate systems for another six decades. NIST and NOAA's National Geodetic Survey jointly deprecated the US Survey Foot effective 1 January 2023, after a public-comment process that began in October 2019; from that date the international foot of exactly 0.3048 m is the sole legally-recognised foot in the United States.

Aviation is the foot's most prominent surviving professional habitat. ICAO standards record aircraft altitudes in feet worldwide — a typical commercial cruise of 35,000 ft is universally referred to as "flight level 350" (FL350), regardless of whether the surrounding airspace is metric for any other purpose — and pilot training, autopilot logic, certified altimeters, terrain charts and air-traffic-control phraseology all run on feet. Russia and several post-Soviet states held out for metres until the 2010s, when most aligned with ICAO feet, leaving China and North Korea as the conspicuous remaining holdouts for metric vertical separation in controlled airspace. Outside aviation, the foot remains everyday currency in the United States: residential and commercial construction, real estate listings, dimensional lumber, pipe and conduit lengths, ceiling heights, and personal height all default to feet and inches. The petroleum industry — including national oil companies in fully metric jurisdictions — measures drilling depth in feet, a convention inherited from American oilfield equipment and tool joints. The United Kingdom officially metricated for trade in 2000 but still posts low-bridge and tunnel-clearance signs in feet and inches alongside metres, and personal height is still quoted in feet and inches across casual British, Irish and Canadian usage. American football and Canadian football mark out the field in yards and feet (the 100-yard playing field plus two 10-yard end zones is 360 ft from end-line to end-line).

One centimetre (cm) is exactly 0.01 metre — one hundredth of the SI base unit of length — and equivalently exactly 10 millimetres. Because the metre is itself defined by fixing the speed of light in vacuum at 299,792,458 m/s and the second by the unperturbed ground-state hyperfine transition of caesium-133, the centimetre is anchored to those same fundamental constants of nature, with no measurement uncertainty in the conversion to or from metres. The cubic centimetre, written cm³, is exactly equal to one millilitre by SI definition: the symbols cm³, cc and mL all denote the same unit of volume, and the older "cc" form survives in medical dosing and automotive engine-displacement contexts (a 50 cc syringe, a 1500 cc engine) even though the cm³ or mL form is preferred in modern scientific publishing. The square centimetre (cm²) is the human-scale SI submultiple of area, with 1 cm² equal to exactly 100 mm² and 10⁻⁴ m². Within SI's own hierarchy the centimetre sits as a recognised but non-preferred submultiple — the BIPM SI Brochure formally prefers prefixes that change the unit by a factor of one thousand — but its everyday use across clothing, healthcare, education and consumer goods has kept it in mainstream international currency despite the formal preference for millimetres.

The centimetre is a metric submultiple — a unit not so much invented as inherited. It entered law as part of the Système Métrique Décimal codified by France's Loi du 18 germinal an III, dated 7 April 1795, the same revolutionary metric statute that defined the metre, the gramme and the litre and laid down the standard prefixes for decimal multiples and submultiples. From that single act the centimetre followed automatically as one hundredth of a metre, with no separate definitional decree ever required for the unit itself. The name is a Latin-Greek compound: centi- from the Latin centum, "hundred", attached to mètre — a hybrid that spread with the metric system through nineteenth-century continental Europe and on through colonial and post-colonial metrication into nearly every national education and trade system on Earth. The centimetre's curious modern status emerged a century and a half later. When the 11th General Conference on Weights and Measures formalised the modern International System of Units in 1960, the SI's house style settled on prefixes that change a unit by a factor of one thousand — kilometre, metre, millimetre, micrometre — relegating the centimetre, a prefix-of-100, to the status of a recognised but non-preferred submultiple. European, Japanese and Korean mechanical-drawing standards have favoured the millimetre across virtually all engineering practice since. Despite that codified preference, the centimetre survives in clothing, medical records and school rulers — the millimetre is too fine for those uses and the metre too coarse, and the centimetre lands at the natural visual scale of the human body.

The centimetre is the everyday human-scale unit of length in nearly every country on Earth except the United States, with three industries giving it particular weight. Garment retail and tape measures: international apparel sizing under ISO 3635 ("Size designation of clothes — Definitions and body measurement procedure") specifies all body measurements — bust, waist, hip, inside leg, sleeve — in centimetres, and dual-scale fabric tape measures sold worldwide carry centimetres on one edge and inches on the other. Continental European apparel sizes (38, 40, 42 …) and East Asian sizes encode body measurements in cm under different national conventions but never in mm: a women's "size 38" in the German Hohenstein system corresponds to an 84 cm bust. Bespoke tailors, pattern-cutting schools and industrial sewing machines all dimension to the centimetre or half-centimetre rather than to the millimetre, the centimetre's coarser grain matching the natural compressibility of fabric on the body. Medical and clinical practice: the WHO Multicentre Growth Reference Study standards published in 2006, adopted by virtually every national paediatric service, chart infant length, child stature and head circumference in centimetres, with the percentile curves drawn on cm-graduated paper from birth through nineteen years of age. Wound measurement in nursing protocols, anatomical dissection, surgical specimen reporting, dermatology lesion sizing and ophthalmology pupillary distance all default to centimetres or millimetres; clinicians read tape-measured circumferences (head, abdomen, mid-arm) in cm, and electronic health-record systems store the values in cm by convention. Primary education: the centimetre is the first SI unit most schoolchildren outside the United States meet on a ruler. The standard 30 cm primary-school ruler used across the United Kingdom, the European Union, India, Japan and most of the rest of the world carries cm numerals zero through thirty along one edge and millimetre subdivisions along the other, and the cm-versus-mm distinction — that ten little marks make one numbered division — is one of the foundational mathematics-curriculum lessons taught at around age six. Beyond those three industries, the centimetre dominates personal measurements (adult height, fitness records), consumer-product packaging dimensions, residential furniture sizing, geography textbooks and weather-radar precipitation totals. The salient absence is professional engineering and architecture: European, Japanese and Korean mechanical drafting standards dimension in millimetres regardless of object size, and architectural plans across the continent dimension building elements in mm and site plans in m, leaving the centimetre largely missing from formal drawings despite its everyday ubiquity outside them.