Length is a base dimension in the International System of Units. The SI unit of length is the meter, defined as the length of the path traveled by light in vacuum during a time interval of $\frac{1}{299792458}$ second (17th CGPM, 1983).

Maple knows the units of length listed in the following table.

An asterisk ( * ) indicates the default context, an at sign (@) indicates an abbreviation, and under the prefixes column, SI indicates that the unit takes all SI prefixes, IEC indicates that the unit takes IEC prefixes, and SI+ and SI- indicate that the unit takes only positive and negative SI prefixes, respectively.  Refer to a unit in the Units package by indexing the name or symbol with the context, for example, meter[SI] or ft[standard]; or, if the context is indicated as the default, by using only the unit name or symbol, for example, meter or ft.

The units of length are defined as follows.

A bohr is defined as $5.291772573\times {10}^{\mathrm{-11}}$ meter.

For each of the following units, there is defined both a standard and US survey unit, each being the appropriate inch.

A standard inch is defined as $2.54$ centimeters.

A US survey inch is defined such that a meter is 39.37 US survey inches.

A mil is defined as $\frac{1}{1000}$ inch.

A line is defined as $\frac{1}{12}$ inch.

A barleycorn is defined as $\frac{1}{3}$ inch.

A digit is defined as $0.75$ inch.

A nail is defined as $2.25$ inches.

A palm is defined as $3$ inches.

A hand is defined as $4$ inches.

A finger is defined as $4.5$ inches.

A span is defined as $9$ inches.

A foot is defined as $12$ inches.

A cubit is defined as $1.5$ feet.

A step is defined as $2.5$ feet.

A yard is defined as $3$ feet.

An ell is defined as $3.75$ feet.

A pace is defined as $5$ feet.

A fathom is defined as $6$ feet.

The rod, pole, and perch are defined as $16.5$ feet.

A furlong is defined as $660$ feet.

A mile is defined as $5280$ feet.

A league is defined as $3$ miles.

A Gunter chain is defined as $66$ feet.

A Gunter link is defined as $\frac{1}{100}$ Gunter chain.

A Ramsden chain is defined as $100$ feet.

A Ramsden link is defined as $\frac{1}{100}$ Ramsden chain, or $1$ foot.

For the following units, the context of the inch, foot, and mile is standard.

A UK nautical chain is defined as $15$ feet.

A US nautical cable is defined as $720$ feet.

A UK nautical cable is defined as $\frac{1}{10}$ nautical mile.

A nautical mile is defined as $1852$ metres.

A nautical league is defined as $3$ nautical miles.

A printer's point is defined as $0.013837$ inch.

A computer point is defined as $\frac{1}{72}$ inch.

A TeX point is defined such that there are $72.27$ points in an inch.

A pica is defined as $12$ points of the corresponding context.

An astronomical unit is defined as $149597870691$ meters.

A parsec is defined as a parallax second based on the astronomical unit.

A Julian or tropical light year is defined as the distance light travels in $1$ Julian or tropical year.

A Julian or tropical hubble is defined as $1.\times {10}^9$ Julian or tropical light years.

A spat is defined as $1.\times {10}^{12}$ meters, or $1$ terameter.

An angstrom is defined as $1.\times {10}^{\mathrm{-10}}$ meters, or $100$ picometers.

A fermi is defined as $1.\times {10}^{\mathrm{-15}}$ meters, or $1$ femtometer.

A micron is another term for a micrometer.

A bicron is another term for a picometer.

The copper and molybdenum x-units are approximately $1.00207789\times {10}^{\mathrm{-13}}$ and $1.00209938\times {10}^{\mathrm{-13}}$ meters, respectively.

A microinch is defined as $1.\times {10}^{\mathrm{-6}}$ inch.

A calibre is defined as $\frac{1}{100}$ inch.

A marathon is defined as $26$ miles and $385$ yards.

A quadrant is defined as $1.\times {10}^7$ meters.

A electrical quadrant is defined as $1.\times {10}^{\mathrm{-11}}$ meter.

A planck length is defined as the square root of: the planck constant times the Newtonian gravitational constant, divided by twice $\mathrm{\pi }$ times the third power of the speed of light.

$\mathrm{convert}\left('\mathrm{meter}'\,'\mathrm{dimensions}'\right)$

$\mathrm{length}$

$\mathrm{convert}\left(1\,'\mathrm{units}'\,'\mathrm{feet}'\,'\mathrm{meters}'\right)$

$\frac{381}{1250}$

$\mathrm{convert}\left(5.2\,'\mathrm{units}'\,'\mathrm{light\_years}'\,'\mathrm{meters}'\right)$

$4.919579846\times {10}^{16}$