angstrom (∆) | Length | Metric | unit of measurement of the wavelength of light | 1 angstrom (∆) = 3.28e-10 feet (ft) | 1 angstrom (∆) = 1.0e-10 metres (m) |

arpent (Quebec) | Length | Canadian, French | One of five old french units that are allowed to be used in Canada | 1 arpent (Quebec) = 191.835feet (ft) | 1 arpent (Quebec) = 58.47 metres (m) |

astronomical unit (au) | Length | Astronomical | One astronomical unit (au) is equal to the average distance between the Earth and the Sun | 1 astronomical unit (au) = 4.908e+11 feet (ft) | 1 astronomical unit (au) = 1.496e+11 metres (m) |

atomic unit of length (a0) | Length | Atomic | a unit in the electron's world. One atomic unit of length, a physical constant, equal to the radius of a Bohr | 1 atomic unit of length (a0) = 1.736e-10 feet (ft) | 1 atomic unit of length (a0) = 5.292e-11 metres (m) |

attometre (am) | Length | Metric | atto was added to the metric prefixes in 1964 | 1 attometre (am) = 3.281e-18 feet (ft) | 1 attometre (am) = 1.0e-18 metres (m) |

cable length (cbl) | Length | Imperial | a measure used at sea by naval authorities | 1 cable length (cbl) = 6.076e+02 feet (ft) | 1 cable length (cbl) = 1.852e+02 metres (m) |

centimetre (cm) | Length | Metric | the centimetre (cm) was the base unit in the CGS system of units | 1 centimetre (cm) = 0.0328 feet (ft) | 1 centimetre (cm) = 0.01 metres (m) |

chain (ch) | Length | Imperial | a length unit used by surveyors | 1 chain (ch) = 66 feet (ft) | 1 chain (ch) = 20.1168 metres (m) |

chain (ch) U.S. survey | Length | US Customary | unit used by surveyors based on the US survey foot | 1 chain (ch) U.S. Survey = 66.000132 feet (ft) | 1 chain (ch) U.S. Survey = 20.11684 metres (m) |

decametre (dam) | Length | Metric | rarely used metric length measurement. | 1 decametre (dam) = 32.8 feet(ft) | 1 decametre (dam) = 10 metres (m) |

decimetre (dm) | Length | Metric | rarely used metric length measurement. | 1 decimetre (dm) = 0.328 feet (ft) | 1 decimetre = 0.1 metres (m) |

exametre (Em) | Length | Metric | exa was added to the metric prefixes in 1975 | 1 exametre (Em) = 3.281e+18 feet (ft) | 1 exametre (Em) = 1.0e+18 metres (m) |

femtometre (fm) | Length | Metric | femto was added to the metric prefixes in 1964 | 1 femtometre (fm) = 3.281e-15 feet (ft) | 1 femtometre (fm) = 1.0e-15 metres (m) |

foot (ft) | Length | Imperial | one Imperial foot (ft) equals 0.999998 foot (ft) U.S. survey | 1 foot (ft) = 12 inches (in) | 1 foot (ft) = 0.3048 metres (m) |

foot (ft) U.S. survey | Length | US Customary | Measurement used in land surveying in the US | 1 foot (ft) U.S. Survey = 1.000002 feet (ft) | 1 foot (ft) U.S. Survey = 0.3048006096 metres (m) |

french foot (Quebec) | Length | Canadian, French | french foot = pied = 12.789 inches. One of five permitted old French units in Canada | 1 french foot (Quebec) = 1.06575feet (ft) | 1 french foot (Quebec) = 0.3248406metres (m) |

french perch (Quebec) | Length | Canadian, French | Perche, a Quebec land measure equal to 18 french feet | 1 french perch (Quebec) = 19.1835 feet (ft) | 1 french perch (Quebec) = 5.847 metres (m) |

furlong (fur) | Length | Imperial | Is used to describe the various distances at a horse race. the Imperial furlong (fur) = 0.999998 furlongs (fur) U.S. survey | 1 furlong (fur) = 660 feet (ft) | 1 furlong (fur) = 201.168 metres (m) |

furlong (fur) U.S. survey | Length | US Customary | based on US survey foot | 1 furlong (fur) U.S. Survey = 660.00132 feet (ft) | 1 furlong (fur) U.S. Survey = 201.1684 metres (m) |

gigametre (Gm) | Length | Metric | Giga is derived from the greek word "gigas" giant | 1 gigametre (Gm) = 3.28e+09 feet (ft) | 1 gigametre (Gm) = 1.0e+09 metres (m) |

hand (hh) | Length | Imperial | used in measuring the height of a horse | 1 hand (hh) = 0.33333 feet (ft) | 1 hand (hh) = 0.1016 metres (m) |

hectometre (hm) | Length | Metric | one hectometre is the side length of a square hectare, equal to 100 metres | 1 hectometre (hm) = 328.084 feet (ft) | 1 hectometre (hm) = 100 metres (m) |

inch (in) | Length | Imperial | traditionally the width of a thumbnail | 1 inch (in) = 0.08332 feet (ft) | 1 inch (in) = 0.0254 metres (m) |

kilometre (km) | Length | Metric | used for measuring larger distances, odometer | 1 kilometre (km) = 3280.84 feet (ft) | 1 kilometre (km) = 1000 metres (m) |

league (lea) U.S. survey | Length | US Customary | land league, a rarely used measurement based on the US survey foot | 1 league (lea) U.S. Survey = 15840.032 feet | 1 league (lea) U.S. Survey = 4828.04 metres (m) |

league (lea) land | Length | Imperial | the land league equals 3 miles (mi) | 1 league (lea) land = 15840 feet (ft) | 1 league (lea) land = 4828.032 metres (m) |

link (li) | Length | Imperial | a length measurement used in land surveying | 1 link (li) = 0.66 feet (ft) | 1 link (li) = 0.201168 metres (m) |

megametre (Mm) | Length | Metric | Mega means large derived from the Greek word "megas" | 1 megametre (Mm) = 3.2808e+06 feet (ft) | 1 megametre (Mm) = 1.0e+06metres (m) |

metre (m) | Length | Metric | metre (m) is a base unit in the Metric system | 1 metre (m) = 3.28084 feet (ft) | 1 metre (m) = 1000 millimetres (mm) |

micrometre (µm) | Length | Metric | The micrometre was previously known as micron | 1 micrometre (µm) = 3.2808e-06 feet (ft) | 1 micrometre (µm) = 0.000001metres (m) |

mile (mi) | Length | Imperial | used as a distance measurement and as a speed unit, miles per hour | 1 mile (mi) = 5280 feet (ft) | 1 mile (mi) = 1609.344 metres (m) |

mile (mi) U.S. survey | Length | US Customary | based on US survey foot. one International mile = 0.999998 mile (mi) U.S. Survey | 1 mile (mi) U.S. Survey = 5280.01056 feet (ft) | 1 mile (mi) U.S. Survey = 1609.34721869 metres (m) |

millimetre (mm) | Length | Metric | unit of length equal to one thousand of a metre | 1 millimetre = 3.2808e-03 feet (ft) | 1 millimetre = 0.001 metres (m) |

nanometre (nm) | Length | Metric | Used in nanotechnology, the study and application of extremely small things | 1 nanometre (nm) = 3.2808e-09 feet (ft) | 1 nanometre (nm) = 1.0e-09 metres (m) |

natural unit of length | Length | Natural | a physical unit of measurement based only on a universal physical constant. | 1 natural unit of length = 1.267e-12 feet (ft) | 1 natural unit of length = 3.862e-13 metres (m) |

nautical mile (nmi) | Length | Imperial | was defined as one minute of latitude along any line of longitude, now one nautical mile (nmi) = 1852 metres (m) | 1 nautical mile (nmi) = 6076.12 feet (ft) | 1 nautical mile (nmi) = 1852 metres |

petametre (Pm) | Length | Metric | peta was added to the metric prefixes in 1975 | 1 petametre (Pm) = 3.28e+15feet (ft) | 1 petametre (Pm) = 1.0e+15 metres (m) |

picometre (pm) | Length | Metric | a picometre used to be called a micromicron | 1 picometre (pm) = 3.2808e-12 feet (ft) | 1 picometre (pm) = 1.0e-12 metres (m) |

planck length (LP) | Length | Planck | smallest measurable length | 1 planck length (LP) = 5.303e-35 feet (ft) | 1 planck length (LP) = 1.616255e-35 metres (m) |

rod (rd) | Length | Imperial | length unit that is the same as a pole | 1 rod (rd) = 16.5 feet (ft) | 1 rod (rd) = 5.0292 metres (m) |

rod (rd) U.S. survey | Length | US Customary | measure based on the US survey foot.rod = perch | 1 rod (rd) U.S. Survey = 16.500033 feet (ft) | 1 rod (rd) U.S. Survey = 5.02921005842 metres (m) |

thou (th) | Length | Imperial | equal to one thousandth of an inch. Mil in the US | 1 thou (th) = 8.3332E-05 feet (ft) | 1 thou (th) = 0.0000254 metres (m) |

yard (yd) | Length | Imperial | the Imperial metre | 1 yard (yd) = 3 feet (ft) | 1 yard (yd) = 0.9144 metres (m) |

yoctometre (ym) | Length | Metric | a yoctometre is about as long as the diameter of a Neutrino, a neutral subatomic particle | 1 yoctometre (ym) = 3.2808e-24 feet (ft) | 1 yoctometre (ym) = 1.0e-24 metres (m) |

yottametre (Ym) | Length | Metric | Yotta is the largest decimal unit prefix in the metric system | 1 yottametre (Ym) = 3.28e+24 feet (ft) | 1 yottametre (Ym) = 1.0e+24 metres (m) |

zeptometre (zm) | Length | Metric | zepto was added to the metric prefixes in 1991 | 1 zeptometre (zm) = 3.2812e-21 feet (ft) | 1 zeptometre (zm) = 1.0e-21 metres (m) |

zettametre (Zm) | Length | Metric | zetta was added to the metric prefixes in 1991 | 1 zettametre (Zm) = 3.28e+21 feet (ft) | 1 zettametre (Zm) = 1.0e+21 metres (m) |