Length Converter

Convert between different length units quickly and accurately.

Value

From

Result

0.394

Inches (in)

Common Length Conversions

1 inch = 2.54 cm

1 foot = 30.48 cm

1 meter = 3.281 ft

1 mile = 1.609 km

Frequently Asked Questions

How do I convert centimeters to inches?

To convert cm to inches, divide the centimeter value by 2.54. For example, 100 cm = 100/2.54 = 39.37 inches.

What is the relationship between meters and feet?

1 meter equals 3.28084 feet. This is useful for international construction and engineering projects.

How many kilometers are in a mile?

1 mile equals 1.60934 kilometers. This conversion is commonly needed when traveling internationally or comparing distances.

Length conversion is one of the most common everyday math tasks, from reading a US recipe in milliliters to checking a property listing that mixes feet and meters. The length-converter on this page switches between the metric system (millimeter, centimeter, meter, kilometer) and the imperial / US customary system (inch, foot, yard, mile) in a single step, with the factors built in so the arithmetic never has to be done by hand.

Metric and imperial are built on different reference points. The meter was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole, and is now locked to the speed of light. The inch has been standardized at exactly 25.4 millimeters since the 1959 international yard and pound agreement, and the foot at 0.3048 meters. Those two anchors are the basis for every conversion on the form: 1 cm = 0.3937 in, 1 m = 3.2808 ft, 1 km = 0.6214 mi, and 1 mi = 1.6093 km.

Several specialized units show up in technical contexts. A nautical mile (nmi), used in aviation and marine navigation, is 1,852 m by international definition and represents one minute of arc along a meridian. A light-year (ly) is not a time unit but a length: the distance light travels in one Julian year, about 9.461 × 10¹² km. Large engineering and astronomy values are usually written in scientific notation to keep the digits readable, and the same approach works for very small measurements such as microns (1 µm = 0.001 mm).

For practical use, type a value in any of the supported fields; the other units update at the same precision. A height of 5 ft 9 in, for example, is 175.26 cm or 1.7526 m, and a 10K race distance of 10 km is 6.2137 mi. The converter keeps the same number of significant figures throughout, so a 1 mm input shows as 0.04 in rather than rounding to a whole inch.

How to use

Enter a value in any field (metric, imperial, or specialty units like nautical miles or light-years).
Read the matching values in the other units, updated automatically to the same precision.
Use the swap or clear controls to start a new conversion without reloading the page.
For very large or very small distances, switch the display to scientific notation to keep the digits compact.

Formula

1 inch = 25.4 mm = 2.54 cm. 1 foot = 0.3048 m. 1 yard = 0.9144 m. 1 mile = 1.609344 km. 1 nautical mile = 1,852 m. 1 light-year ≈ 9.4607 × 10¹² km.

Interpreting your results

Metric units scale by powers of ten, so converting within metric is just shifting the decimal: 1 m = 100 cm = 1,000 mm = 0.001 km. Imperial units do not scale that cleanly (12 in = 1 ft, 3 ft = 1 yd, 5,280 ft = 1 mi), which is where errors tend to creep in. For navigation, remember that knots already include time, so a speed of 10 knots is 10 nmi per hour, not 10 nmi alone. For astronomy, light-years are usually paired with parsecs (1 pc ≈ 3.262 ly) when comparing to professional literature.

Frequently asked questions

How many centimeters are in an inch?

One inch equals exactly 2.54 centimeters. This has been the international standard since 1959 and is the figure used throughout the converter. For quick mental math, 1 cm is roughly 0.39 in, so 10 cm is just under 4 inches.

What is the difference between a nautical mile and a statute mile?

A statute (land) mile is 1,609.344 m, while a nautical mile is 1,852 m. The nautical mile equals one minute of latitude on a meridian, which makes it convenient for charts and air traffic routes. Speeds at sea and in the air are quoted in knots (nautical miles per hour), not mph.

How do I convert feet and inches to centimeters?

Multiply the feet by 30.48, multiply the inches by 2.54, then add the two results. A height of 5 ft 9 in, for example, is 5 × 30.48 + 9 × 2.54 = 152.4 + 22.86 = 175.26 cm. The converter on this page accepts either form.

Is a light-year a unit of time?

No. A light-year is a unit of distance, defined as the distance light travels in a vacuum over one Julian year, about 9.46 trillion kilometers. The closest star, Proxima Centauri, is about 4.24 light-years from the Sun, so its light seen now left the star just over four years ago.