Length Converter for Metric and Imperial Units Online
Convert millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles with instant results and common unit shortcuts.
Convert Length
Enter a value, choose the starting unit, and select the unit you want.
How to Use the Length Converter
The length converter changes a measurement from one unit to another. Enter a value, choose the starting unit, then select the unit you want to receive. The result updates instantly.
- Enter the length. Type zero or any positive number.
- Choose the starting unit. Select millimeters, centimeters, meters, kilometers, inches, feet, yards, or miles.
- Choose the target unit. The converted value appears immediately.
- Use Swap Units when needed. This reverses the two selected units.
- Check the other-unit results. The tool also shows the same length across all eight supported units.
Popular shortcuts make common conversions such as centimeters to inches, meters to feet, and kilometers to miles faster to select.
How Length Conversion Works
Length conversion is based on fixed relationships between measurement units. The tool converts the entered value to meters first, then converts that meter value into the selected target unit.
Value in meters = Input Value × Source Unit Factor
Converted Value = Value in meters ÷ Target Unit Factor
Using one base unit keeps the calculation consistent across every supported pair instead of relying on a separate formula for each combination.
Length Conversion Formula
A conversion factor tells you how much of one unit equals another. For example, one inch equals exactly 0.0254 meters, so inches can be converted to meters by multiplying by 0.0254.
Meters = Inches × 0.0254
To convert meters back to inches, divide by 0.0254.
Inches = Meters ÷ 0.0254
Metric Length Units
The metric system uses decimal relationships, so units scale by powers of ten. The meter is the SI base unit of length. The most common metric length units used in this tool are millimeters, centimeters, meters, and kilometers.
- 10 millimeters = 1 centimeter
- 100 centimeters = 1 meter
- 1,000 meters = 1 kilometer
- 1 meter = 1,000 millimeters
This decimal structure makes many metric conversions possible by shifting the decimal point.
Imperial and US Length Units
Inches, feet, yards, and miles use different relationships from metric units. The standard international inch and foot are defined in relation to the meter.
- 12 inches = 1 foot
- 3 feet = 1 yard
- 1,760 yards = 1 mile
- 5,280 feet = 1 mile
- 1 inch = exactly 2.54 centimeters
- 1 foot = exactly 0.3048 meters
Common Length Conversion Chart
| Starting Unit | Equivalent Length |
|---|---|
| 1 centimeter | 10 millimeters |
| 1 meter | 100 centimeters |
| 1 kilometer | 1,000 meters |
| 1 inch | 2.54 centimeters |
| 1 foot | 12 inches |
| 1 yard | 3 feet |
| 1 mile | 5,280 feet |
| 1 mile | 1.609344 kilometers |
How to Convert Centimeters to Inches
Because one inch equals exactly 2.54 centimeters, divide the centimeter value by 2.54.
Inches = Centimeters ÷ 2.54
30 cm to inches
30 ÷ 2.54 = 11.811024 inches
How to Convert Inches to Centimeters
Multiply inches by 2.54 because one inch is exactly 2.54 centimeters.
Centimeters = Inches × 2.54
12 inches to centimeters
12 × 2.54 = 30.48 cm
How to Convert Meters to Feet
One foot equals exactly 0.3048 meters. Divide meters by 0.3048 to get feet.
Feet = Meters ÷ 0.3048
1.8 meters to feet
1.8 ÷ 0.3048 = 5.905512 feet
When feet are selected as the target unit, the calculator also gives a feet-and-inches style result for practical use.
How to Convert Feet to Meters
Multiply the number of feet by 0.3048.
Meters = Feet × 0.3048
10 feet to meters
10 × 0.3048 = 3.048 meters
How to Convert Kilometers to Miles
One mile equals exactly 1.609344 kilometers. Divide kilometers by 1.609344 to calculate miles.
Miles = Kilometers ÷ 1.609344
5 kilometers to miles
5 ÷ 1.609344 = 3.106856 miles
How to Convert Miles to Kilometers
Multiply miles by 1.609344 to convert the distance to kilometers.
Kilometers = Miles × 1.609344
10 miles to kilometers
10 × 1.609344 = 16.09344 kilometers
Metric vs Imperial Length Measurement
Metric units are based on decimal scaling. Millimeters, centimeters, meters, and kilometers move in powers of ten. This makes many metric calculations straightforward.
Imperial and US customary length units use relationships such as 12 inches per foot, 3 feet per yard, and 1,760 yards per mile. A unit converter is useful when moving between these systems because the relationships are not decimal.
Common Length Conversion Mistakes
- Using area units in a length calculation. Square meters and square feet measure area, not length.
- Confusing feet with feet and inches. A decimal value such as 5.5 ft means 5 feet 6 inches, not 5 feet 5 inches.
- Rounding too early. Keep more precision during the calculation and round the final result.
- Reversing the conversion factor. Multiplying when the formula requires division can produce a large error.
- Mixing miles and kilometers. One mile is longer than one kilometer, so a mile value converts to a larger kilometer number.
Length Converter FAQs
What units does this length converter support?
It supports millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles.
How many centimeters are in one inch?
One inch equals exactly 2.54 centimeters.
How many feet are in one meter?
One meter is approximately 3.28084 feet.
How many kilometers are in one mile?
One mile equals exactly 1.609344 kilometers.
Can the converter show feet and inches?
Yes. When feet are selected as the target unit, the tool also shows an approximate feet-and-inches result.
Does the tool support negative lengths?
No. The page is designed for physical length and distance, so it accepts zero and positive values.
Is a mile exactly 1.609344 kilometers?
Yes. Using the international foot definition, one international mile is exactly 1,609.344 meters, which is 1.609344 kilometers.
Sources and Calculation Methodology
Conversion definitions reviewed September 13, 2026.
The calculator uses the meter as its internal base unit. Metric values are converted through standard SI relationships, while inches, feet, yards, and miles use the international definitions tied to the meter.
- BIPM: SI Base Unit, Metre
- BIPM: International System of Units
- NIST: SI Units, Length
- NIST: Guide to SI Conversion Factors
For other measurement types, use the Weight Converter, Temperature Converter, or Volume Converter.