Length Converter

Enter a non-negative length, select its current unit, and choose the unit you want to convert to.

Use Swap to reverse the conversion. When a valid result exists, the unrounded converted value becomes the new source value.

The input supports ordinary decimals, grouped values such as 10,000, and scientific notation such as 2.5e6.

Each supported unit has a factor representing how many metres it contains.

The source value is multiplied by its metres-per-unit factor and divided by the target unit's factor.

Using the metre as the common reference prevents conversions from being chained through visibly rounded intermediate values.

The metre, symbol m, is the SI base unit of length.

Its modern definition fixes the speed of light in vacuum at exactly 299,792,458 metres per second.

Metric prefixes scale the metre by powers of ten. One millimetre is 0.001 metre, one centimetre is 0.01 metre, and one kilometre is 1,000 metres.

Moving between metric length units changes the decimal position without changing the measured distance.

The international inch equals exactly 0.0254 metre, or 2.54 centimetres.

One international foot contains exactly 12 inches and equals 0.3048 metre.

One international yard contains exactly three feet and equals 0.9144 metre.

These exact relationships are used for every inch, foot, and yard conversion in the calculator.

The international mile equals exactly 5,280 international feet.

Because the international foot is exactly 0.3048 metre, one international mile equals exactly 1,609.344 metres or 1.609344 kilometres.

Miles are commonly used for road, travel, running, and geographic distances in countries that retain mile-based conventions.

The international nautical mile equals exactly 1,852 metres.

It is used for marine navigation and widely used for aviation distance.

One nautical mile is approximately 1.1508 international miles.

A nautical mile must remain explicitly labelled because it is longer than an ordinary international statute mile.

This converter uses the international foot of exactly 0.3048 metre.

The former U.S. survey foot was slightly longer and should now be avoided except when working with historic or legacy data.

Older land surveys, coordinate systems, maps, and engineering records may still specify survey-foot-based measurements.

For legal surveying or geospatial transformation, use the exact unit definition attached to the source dataset rather than assuming every value marked ft uses the same historic standard.

Construction, hardware, machining, and product dimensions often express inches as common fractions.

Convert a fraction to decimal inches before entering it. For example, ¼ inch is 0.25 inch, ½ inch is 0.5 inch, and ¾ inch is 0.75 inch.

The table shows common fractional-inch values and their exact millimetre equivalents.

The table uses the same exact conversion factors as the live calculator.

Non-terminating results are rounded to no more than four decimal places.

The most useful unit depends on the measurement scale, field, region, instrument, and source document.

Changing units alters only the numerical representation. It does not improve the accuracy of the original measurement.

Length describes the extent of an object or interval.

Distance commonly describes separation or the path travelled, but it has the same physical dimension as length.

The converter can restate either quantity when its numeric value is already known.

It does not determine the shortest route, driving distance, map distance, or curved path between locations.

A linear conversion factor applies only to one-dimensional length.

Area conversion squares the linear factor, while volume conversion cubes it.

For example, one foot equals 0.3048 metre, but one square foot equals 0.3048² square metre and one cubic foot equals 0.3048³ cubic metre.

Do not use this length converter to convert square or cubic measurements.

The underlying unit factors remain unrounded during calculation.

Ordinary results display up to four decimal places, while extremely small or large results may use scientific notation.

An exact conversion factor does not make the original measurement exact.

Instrument resolution, measurement technique, source rounding, temperature effects, tolerances, and data quality still determine practical accuracy.

Length conversion runs entirely in the browser.

Entered values and selected units are not uploaded, added to a public URL, or permanently stored.

Clipboard access is requested only when the result copy control is used.