Length converter

Length conversion table

How to convert length units

Most length conversions follow a simple multiplication by a fixed factor. To convert from one unit to another, multiply the value by the ratio between the two units.

Centimeters to inches

inches = centimeters × 0.3937007874

Example: 30 cm = 30 × 0.3937007874 = 11.811 in

Kilometers to miles

miles = kilometers × 0.6213711922

Example: 10 km = 10 × 0.6213711922 = 6.2137 mi

Meters to feet

feet = meters × 3.280839895

Example: 5 m = 5 × 3.280839895 = 16.404 ft

Popular real-world length examples

Length conversion becomes easier when you can connect units to familiar distances and objects.

Earth to Sun distance

The average distance from the Earth to the Sun is about 149.6 million kilometers, which is also about 92.96 million miles. In astronomy this average distance is called 1 astronomical unit (AU).

Marathon distance

A full marathon is 42.195 kilometers, which equals 26.2188 miles. This is one of the most commonly searched long-distance conversions.

Human height

Human height is often converted between centimeters and feet/inches. For example, 180 cm is about 5.9055 feet, which is commonly expressed as 5 ft 10.9 in.

Road distances

Most countries use kilometers for road signs and navigation, while the United States and United Kingdom commonly use miles. A practical reference is that 10 kilometers is about 6.21 miles, and 50 miles is about 80.47 kilometers.

Aircraft altitude

Aircraft cruising altitude is usually expressed in feet. A cruising altitude of 35,000 ft is about 10,668 meters or 10.668 kilometers.

How very large distances are measured

Different units become useful at different scales.

Everyday distances

For room sizes, furniture, body measurements, and small objects, centimeters, inches, feet, and meters are usually the most practical units.

City and travel distances

For driving, running, cycling, and mapping, kilometers and miles are the standard units because meters or feet become too granular for longer travel.

Scientific and industrial scales

Very small distances are often measured in millimeters, micrometers, and nanometers. These units are common in manufacturing, biology, optics, and electronics.

Astronomical distances

Extremely large distances between stars are too large to express conveniently in meters or miles. That is why astronomy often uses astronomical units, light years, and parsecs. In this converter, light years help put huge interstellar distances into a more understandable form.

How humans measured distance before modern standards

Before international standards existed, people often measured length using the human body and local references.

Body-based measurement

Units such as the foot, inch, cubit, hand, and pace all began as practical body-based approximations. They were easy to use, but they were not consistent from one place to another.

Land and travel measurement

Longer distances were often estimated using walking time, horse travel, or local landmarks. This worked for daily life, but it created problems for trade, science, engineering, and taxation.

Standardization

The metric system solved this by introducing decimal units tied to a universal standard. Later, improved science allowed the meter to be defined using the speed of light, making modern measurement far more precise than historical physical objects or regional customs.

Why length conversions matter

Length conversions are used constantly across industries and everyday life.

Construction and engineering

Building plans, material sizes, and tolerances often need quick conversion between metric and imperial measurements.

Travel and navigation

People convert miles to kilometers and kilometers to miles when reading maps, booking trips, comparing driving distances, or training for races.

Shopping and product dimensions

Furniture, TVs, monitors, luggage, clothing measurements, and home improvement products are often listed in different unit systems depending on the seller and country.

Science, education, and research

Students and professionals frequently convert between millimeters, centimeters, meters, micrometers, and nanometers in laboratory, classroom, and technical contexts.