Length Converter Online Free
Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards, miles, and nautical miles instantly. Metric and imperial — no signup, runs entirely in your browser.
All Length Conversions
| Unit | Value |
|---|---|
| Millimeter (mm) | — |
| Centimeter (cm) | — |
| Meter (m) | — |
| Kilometer (km) | — |
| Inch (in) | — |
| Foot (ft) | — |
| Yard (yd) | — |
| Mile (mi) | — |
| Nautical Mile (nmi) | — |
How to Convert Length
- 1Select the source unit from the From dropdown — e.g. meters.
- 2Enter your value. The target unit result updates instantly. Use the swap button (↔) to reverse direction.
- 3Scroll the all conversions table below the input to see the value expressed in every supported unit simultaneously.
Metric and Imperial Length Units
The metric system uses a base-10 scale: 10 mm = 1 cm, 100 cm = 1 m, 1000 m = 1 km. Imperial units (inches, feet, yards, miles) use irregular ratios: 12 in = 1 ft, 3 ft = 1 yd, 1760 yd = 1 mi. The exact relationship between the two systems is 1 inch = 2.54 cm, which is the foundation of all metric–imperial conversions.
Common Length Conversion Reference
| From | To | Multiply by | Example |
|---|---|---|---|
| Inches | Centimeters | 2.54 | 12 in = 30.48 cm |
| Centimeters | Inches | 0.3937 | 30 cm = 11.81 in |
| Feet | Meters | 0.3048 | 6 ft = 1.83 m |
| Meters | Feet | 3.28084 | 2 m = 6.56 ft |
| Miles | Kilometers | 1.60934 | 10 mi = 16.09 km |
| Kilometers | Miles | 0.62137 | 100 km = 62.14 mi |
| Yards | Meters | 0.9144 | 100 yd = 91.44 m |
| Nautical Miles | Kilometers | 1.852 | 5 nmi = 9.26 km |
Quick Mental Length Conversion Tips
km to Miles
Multiply by 0.6 for a quick estimate. More precisely, multiply by 0.621. So 100 km ≈ 62 miles — useful for reading road signs abroad.
cm to Inches
Divide by 2.5 for a rough estimate (exact is 2.54). So 100 cm ÷ 2.5 = 40 in. Actual answer: 39.37 in. Close enough for everyday use.
Height Conversion
To convert height like 5 ft 10 in: multiply feet by 12 and add inches (70 in total), then multiply by 2.54 to get cm. 70 × 2.54 = 177.8 cm.
Meters to Feet
Multiply by 3 for a quick estimate (exact is 3.281). So 10 m ≈ 33 ft. The exact answer is 32.81 ft. Useful for estimating building heights.
Frequently Asked Questions
How do I convert centimeters to inches?
Divide by 2.54. One inch is defined as exactly 2.54 centimeters, so: cm ÷ 2.54 = inches. For example, 30 cm ÷ 2.54 = 11.81 inches. The converter does this calculation automatically.
How many feet are in a meter?
One meter equals approximately 3.28084 feet. Conversely, one foot equals 0.3048 meters exactly. For height conversions like 1.75 m, that is 5 ft 8.9 in (about 5 ft 9 in).
How do I convert kilometers to miles?
Multiply by 0.621371. One kilometer equals approximately 0.6214 miles. So 10 km = 6.21 miles, and 100 km = 62.14 miles. For a quick mental estimate, multiply by 0.6.
What is a nautical mile?
A nautical mile is 1,852 meters (1.852 km) and is used in maritime and aviation navigation. It is based on one minute of arc of latitude along a great circle of the Earth. One nautical mile equals approximately 1.151 statute miles.
Does the converter work offline?
Yes. All conversion factors are embedded in the page JavaScript. Once loaded, you can convert any length value without an internet connection.
Why does my result have many decimal places?
Most length conversions between metric and imperial units produce irrational or recurring fractions. The converter shows up to 8 significant figures for accuracy. For practical use, round to 2–3 decimal places.