Length converter

Enter a value, choose its current unit and select the target unit. The table shows equivalent values within the same physical quantity. Signed values are supported; conversion does not change the meaning of a negative measurement.

1 in = 25.4 mm; 1 mi = 1.609344 km

Length, area and volume are different quantities. Area factors are squared and volume factors are cubed. Millimetres cannot be converted directly to litres; cubic millimetres can. If you meant millilitres, 1000 mL equals 1 L.

Reference: NIST SI conversion factors

The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.

Value

1

From unit

in

To unit

mm

Primary result: Converted value: 25.4 mm.

• Check the selected mode, units and input values before using the result.
• Read the assumptions and rounding rules; compare the worked example with your intended calculation.
• A numerical result does not supply missing context or change the stated limitations.

Results use floating-point arithmetic and are displayed to ten significant digits. This tool does not measure an object, infer missing dimensions or supply material density. Keep unrounded values for further calculations when precision matters.