Length Converter

Type a length, pick the unit you are starting from and the one you want, and the converted value appears instantly. The converter covers the units people actually mix in daily life: metric (millimeters through kilometers) and imperial (inches through miles). Read the result as the same physical distance written a second way — 5 meters and 16.4042 feet are not two lengths but one, expressed in two vocabularies.

How the conversion works

Every unit is stored as an exact factor relative to the meter, so any conversion is two steps: turn the input into meters, then turn meters into the unit you asked for.

result = value × factor_from ÷ factor_to

With the default values — 5 meters into feet — that is 5 ÷ 0.3048 = 16.4042 ft. Because imperial units have been defined in exact metric terms since 1959, none of these factors are approximations: a foot is exactly 0.3048 m, a yard exactly 0.9144 m, a mile exactly 1,609.344 m. The meter sits at the center of the whole table for a reason. It is the only unit here whose definition is anchored to physics rather than to another unit, so pinning everything else to it removes any ambiguity about what a foot or a mile actually means.

A short history of the meter

The meter is a child of the French Revolution. In 1791 the National Assembly, acting on a report from the French Academy of Sciences, adopted a length equal to one ten-millionth of the distance from the North Pole to the Equator, measured along the meridian that runs through Paris. Two astronomers, Jean-Baptiste Delambre and Pierre Méchain, spent six years, from 1792 to 1798, surveying the arc of that meridian between Dunkirk and Barcelona to fix the figure, working through the political disruption of the Revolution as they went. An international commission reviewed their numbers and settled the final value in 1799, and in June of that year a platinum bar cut to the result was deposited in the French national archives. That bar, the mètre des Archives, became the physical reference for the new unit.

The idea spread beyond France. On 20 May 1875 seventeen nations signed the Metre Convention in Paris, an international treaty that made the meter a shared scientific standard and set up the bodies that still govern it. In 1889 the first General Conference on Weights and Measures sanctioned a fresh reference: the International Prototype Metre, a bar of ninety percent platinum and ten percent iridium, with certified copies handed out to member states. For a while a length was, quite literally, a scratch on a metal bar in a vault outside Paris.

A physical object is a fragile thing to hang a global standard on. It can be damaged, and it can drift over decades. So the definition was cut loose from the bar in two stages. In 1960 the 11th General Conference on Weights and Measures redefined the meter as 1,650,763.73 wavelengths of orange-red light emitted by krypton-86, which any properly equipped laboratory could reproduce. Then in 1983 the 17th Conference adopted the definition still in force: the meter is the distance light travels in a vacuum during 1/299,792,458 of a second. That odd denominator was chosen precisely so the new meter matched the old one, which means the 1983 change altered nothing you could detect with a ruler while fixing the speed of light as an exact number by definition.

Where feet, yards and miles come from

The imperial units in this converter are far older and far messier in origin. The foot began, unsurprisingly, as the length of a human foot, a rough measure that every ancient culture used in some form. The Romans standardized theirs: the pes was about 295.7 mm and was divided into twelve unciae. That Latin word uncia, meaning a twelfth part, is the common ancestor of both "inch" and "ounce." The Roman mile was the mille passus, a thousand paces of five Roman feet each, which worked out to roughly 1,479 meters, noticeably shorter than the mile we use now.

Medieval England inherited this jumble and slowly imposed order on it. Tradition holds that Henry I set the yard as the distance from his nose to the tip of his outstretched thumb, a story that is almost certainly apocryphal but captures how bodily and arbitrary early standards were. Successive statutes tightened the definitions. The modern statute mile was fixed under Elizabeth I by an Act of Parliament that received royal assent in April 1593 — a law otherwise concerned with restricting new building in and around London and Westminster, which defined the mile almost in passing as eight furlongs, every furlong forty poles, and every pole sixteen and a half feet. That arithmetic gives 5,280 feet, or 1,760 yards, and it is the mile still printed on road signs across the English-speaking world. The furlong itself takes its name from the Old English for a long furrow, the length of a plowed strip in a medieval field, and it survives today mainly on horse-racing tracks, where eight of them still make a mile.

The 1959 agreement that joined the two systems

For centuries the imperial units were defined by their own physical prototypes, which meant they never quite agreed across borders. The old American inch worked out to about 25.4000508 mm and the British imperial inch to about 25.399977 mm — a gap of roughly two parts in a million, smaller than a ten-thousandth of a millimeter, but enough to matter in precision engineering. The United States had already tied its customary units to metric standards through the Mendenhall Order of 1893, and industry on both sides of the Atlantic had converged on an inch of exactly 25.4 mm well before governments did: the British Standards Institution adopted that figure in 1930 and the American Standards Association followed in 1933. The loose ends were finally knotted on 1 July 1959, when the United States, United Kingdom, Canada, Australia, New Zealand and South Africa signed the International Yard and Pound Agreement, fixing the yard at exactly 0.9144 meters. From that date the foot, the inch and the statute mile all became exact metric quantities, which is why this converter can multiply and divide without ever rounding a factor.

Conversions people look up constantly

The table rounds to six significant digits; the calculator itself keeps full floating-point precision and rounds only for display.

Feet and inches together

The one conversion that trips people up is height, because feet and inches are used together. To convert 5 ft 11 in to centimeters, turn the whole thing into inches first: 5 × 12 + 11 = 71 inches, then 71 × 2.54 = 180.34 cm. Going the other way, 175 cm ÷ 2.54 = 68.9 inches, which is 5 ft 8.9 in — near enough to 5 ft 9. If you convert straight to feet you get a decimal like 5.74 ft, which is correct but useless at a tailor's. When you need the inches part, convert to inches and divide by twelve, keeping the remainder.

When precision actually matters

For everyday questions — is a 180 cm wardrobe taller than my 6 ft ceiling nook? — four decimal places are more than enough. If you are machining parts or doing survey work, be aware that the old US survey foot differs from the international foot by two parts per million. That difference is invisible across a doorway, but it reaches roughly a foot over a hundred miles and about two feet at the million-foot coordinate values common in state plane surveying. That is why the National Institute of Standards and Technology and the National Geodetic Survey deprecated the survey foot on 31 December 2022 in favor of the international foot and the meter. This converter uses the international definitions, which is what every current standard specifies. One more unit worth flagging: the nautical mile used at sea and in aviation was fixed at exactly 1,852 meters by an international hydrographic conference in Monaco in 1929. It descends from the idea of a minute of arc along a meridian, and it is a genuinely different unit from the statute mile in the table above.

Frequently asked questions

How many feet are in a meter?

One meter is 3.2808 feet, or just over 3 feet 3 inches. A quick mental shortcut: multiply meters by 3.3 and you will land within half a percent.

Why is an inch exactly 25.4 mm?

Because it was defined that way. In 1959 the US, UK, Canada, Australia, New Zealand and South Africa signed the International Yard and Pound Agreement, fixing the yard at exactly 0.9144 meters — which makes the inch exactly 25.4 mm. Before that, each country's inch differed by a few millionths.

Is a mile the same everywhere?

The statute mile used on road signs in the US and UK is exactly 1,609.344 meters, and that is what this converter uses. The nautical mile used at sea and in aviation is different — 1,852 meters — and is not the same unit.

Metre or meter — which spelling is right?

Both. Metre is the British, Irish, Australian and Canadian spelling; meter is the American one. The unit is identical, and this site uses the American spelling throughout.