Length Converter

Length Converter

Convert between metric and US customary length units, including millimetres, centimetres, metres, kilometres, inches, feet, yards, and miles. Enter a value in one unit and the converter returns the equivalent in the others.

Conversion factors

Since 1959, the international yard and pound agreement has fixed the customary length units against the metre, so these factors are exact by definition:

• 1 inch = 2.54 cm
• 1 foot = 0.3048 m (12 inches)
• 1 yard = 0.9144 m (3 feet)
• 1 mile = 1.609344 km (5,280 feet)
• 1 nautical mile = 1,852 m (used in aviation and at sea)
• 1 km = 1,000 m, 1 m = 100 cm, 1 cm = 10 mm

To go the other way, divide instead of multiply: for example, 1 cm = 0.393701 in (rounded) because 1 / 2.54 = 0.3937....

Worked example

Suppose a hiking trail is listed as 7.5 miles and you want kilometres:

• 7.5 × 1.609344 = 12.07008, so the trail is about 12.07 km.

Or convert a height of 6 feet 2 inches to centimetres. First express it in inches: 6 × 12 + 2 = 74 in. Then 74 × 2.54 = 187.96, so the height is 187.96 cm, or just under 1.88 m.

When to use this converter

• Travel: road signs and distances are posted in kilometres in most of the world but in miles in the US and UK, so converting helps you judge driving times and fuel stops.
• Online shopping and shipping: parcel dimensions, furniture sizes, and screen measurements are often listed in inches or centimetres depending on the seller's country.
• DIY and construction: plans drawn in metric often need to be matched against lumber, pipe, or fasteners sold in inches and feet.
• Sports and fitness: race distances (5K, 10K, marathon) are metric, while some running apps and treadmills default to miles.

Tips for accurate conversions

• Statute miles and nautical miles are different units. A nautical mile is exactly 1,852 m, about 15% longer than a statute mile, and is the basis for the knot.
• Keep full precision until the final step, then round. Rounding intermediate values, such as using 1.6 instead of 1.609344 for miles to kilometres, compounds the error over long distances.
• Mixed measurements such as 5 ft 8 in should be converted to a single unit (68 inches) before applying a factor.
• Typography points and picas, surveyor's chains, and other specialist units have their own definitions; this converter covers the everyday metric and customary units listed above.
• For very small lengths, remember the metric ladder is strictly decimal: 1 mm = 1,000 µm and 1 m = 1,000 mm, which makes metric-to-metric conversion a matter of shifting the decimal point.

Related calculators

You can convert other quantities with the Weight Converter and the Speed Converter. Other utilities on this site include the Age Calculator, the Case Converter, and the Password Generator.