Length is the measurement people convert most often: a height on a passport form, a screen size in inches, a running distance in miles, a room plan drawn in feet. This converter covers eleven units, from the nanometer to the nautical mile, and updates the answer while you type. There is no Convert button to press and nothing to install.
Beside the main result you get a table of the same length expressed in every other unit, so a single entry answers several questions at once. The arithmetic runs in your browser, which means the page keeps working offline once it has loaded and nothing you type is sent anywhere.
Where the conversion factors come from
Since the international yard and pound agreement of 1959, the inch has been defined as exactly 25.4 millimeters. Everything else in the imperial system follows from that: a foot is 12 inches, or 0.3048 m; a yard is 3 feet, or 0.9144 m; and a statute mile is 1,760 yards, or 1,609.344 m. The nautical mile, used at sea and in aviation, is defined separately as exactly 1,852 m. Because these are exact definitions rather than measurements, a correct converter never needs to round its inputs.
This tool stores every unit as an exact number of meters and converts by multiplying into meters and dividing out again. That is why 1 inch comes out as exactly 2.54 cm and 1 mile as exactly 1.609344 km. Results that never terminate, such as 1 m in feet, are shown to 12 significant digits: 3.28083989501 ft. Values smaller than a billionth or astronomically large switch to scientific notation so they stay readable.
Everyday length conversions
Heights for forms, dating apps and sports
Someone who is 5 feet 10 inches tall is 70 inches, and 70 in converts to exactly 177.8 cm. Going the other way, 1.83 m is a little over 6 ft, since 6 ft is exactly 1.8288 m. Enter the total in inches when a height is given in feet and inches, because the tool takes one number at a time.
Running, cycling and road distances
A 10 km race is 6.21371192237 miles, a marathon of 42.195 km is about 26.22 miles, and road signs in the UK and US quote miles while most maps elsewhere use kilometers. Convert once and keep the table open to compare paces or route lengths.
DIY, furniture and screen sizes
Shelving, timber and tiles are often sold in inches or feet in North America while plans are drawn in millimeters elsewhere. Typing a measurement in millimeters and reading the inch row avoids the classic mistake of mixing up 2.5 and 2.54.
Using the converter and the all-units table
The Value box accepts whole numbers, decimals and scientific notation such as 2.5e-6. A comma works as a decimal separator for people who write 12,5, and Arabic-Indic digits are read correctly too. Pick the starting unit under From and the target unit under To; the result appears immediately in the Result panel with a copy button. The swap button between the two unit menus flips the direction and carries the current answer into the Value box.
Under the result, the All units table lists the same distance in nanometers, micrometers, millimeters, centimeters, meters, kilometers, inches, feet, yards, miles and nautical miles. Clicking a unit name in that table makes it the new target, and each row has its own copy button. Everything is computed on your device, so it is instant even on a slow connection.
Cómo usar esta herramienta
- Type the length you have in the Value box, for example 70.
- Choose its unit in the From menu, such as Inch (in).
- Choose the unit you need in the To menu, such as Centimeter (cm), and read the result.
- Scan the All units table for other units, click a row to make it the target, or use the copy buttons.
Limitations
- Feet and inches cannot be typed as one compound value like 5'10". Convert the total in inches (70) or in decimal feet (5.8333).
- A comma followed by exactly three digits groups thousands, so 1,500 means fifteen hundred; to mean one and a half with a comma, type 1,5. When a value has both, the last comma or dot is the decimal mark, so 1.234,5 and 1,234.5 are the same.
- Results show up to 12 significant digits. That is far beyond the precision of any tape measure, but it is still a rounded display of non-terminating values.
- Historic and regional units, such as the US survey foot or astronomical units like the light-year, are not included.