Length Converter
Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards, miles and more.
What is a length converter?
A length converter translates a measurement from one unit system to another. Whether you are comparing a height in feet to centimeters, calculating how many miles make up a marathon, or working with engineering drawings that mix metric and imperial units, a reliable converter saves time and eliminates manual calculation errors.
All conversions on this page are performed by first converting your input to meters — the SI base unit for length — and then dividing by the target unit's meter factor. This two-step approach ensures consistent accuracy across all unit pairs without needing a separate formula for every combination.
How length conversion works
Each unit has a fixed relationship to the meter. The conversion formula is:
Result = Input × (From unit in meters) ÷ (To unit in meters)Worked examples:
Convert 5 miles to kilometers:
5 × 1609.344 ÷ 1000 = 8.047 km
Convert 6 feet to centimeters:
6 × 0.3048 ÷ 0.01 = 182.88 cm
Convert 100 inches to meters:
100 × 0.0254 ÷ 1 = 2.54 mMetric vs. imperial: key differences
The metric system (formally the International System of Units, SI) uses powers of 10, making conversions within the system straightforward. Imperial units, used primarily in the United States and to some extent in the UK, rely on historical conventions with no consistent multiplier between steps.
| Conversion | Exact value | Common use |
|---|---|---|
| 1 inch → cm | 2.54 cm (exact, by definition) | Screen sizes, clothing, body measurements |
| 1 foot → cm | 30.48 cm | Human height in the US |
| 1 yard → m | 0.9144 m | American football field dimensions |
| 1 mile → km | 1.609344 km | Road distances, running races |
| 1 nautical mile → km | 1.852 km | Aviation and maritime navigation |
Common real-world uses
The nautical mile: why does it exist?
A nautical mile (1,852 m) is based on the circumference of the Earth. One nautical mile equals one arcminute of latitude, which means navigators can directly read distances off a globe or chart using degrees and minutes — without any conversion factor. This is why aviation and shipping still use nautical miles despite the rest of the world adopting metric.
A knot — the unit of speed used at sea and in the air — is one nautical mile per hour. So when an aircraft cruises at 450 knots, it covers 450 nautical miles (roughly 833 km) every hour.
Tips for avoiding conversion mistakes
- Inch ≠ 2.5 cm. The exact value is 2.54 cm. Rounding to 2.5 introduces a 1.6% error — significant when measuring furniture, body dimensions, or precision parts over multiple steps.
- Miles and kilometers are not interchangeable estimates. 1 mile ≈ 1.6 km is a useful mental shortcut, but the true value is 1.609344 km. A 5-mile difference becomes an 8-km difference, not 8.05 — accuracy matters in fuel calculations and routing.
- Feet and meters both describe height, but confusing them is dangerous. A 1990 Airbus A320 crash at Bangalore was partly attributed to altitude confusion between feet and meters. Always confirm which unit a measuring system uses before reading values.
- Area and volume use squared and cubed length units. Converting 3 feet to meters gives 0.914 m. But 3 ft² converts to 0.279 m² (not 0.914²), and 3 ft³ to 0.085 m³. Use a dedicated area or volume converter for those calculations.
Frequently asked questions
How many centimeters are in an inch?
One inch equals exactly 2.54 centimeters. To convert inches to cm, multiply by 2.54.
How do I convert miles to kilometers?
Multiply miles by 1.609. For example, 5 miles × 1.609 = 8.05 kilometers.
How many feet are in a meter?
One meter equals about 3.281 feet. To convert meters to feet, multiply by 3.281.
What is the difference between metric and imperial length?
Metric units (mm, cm, m, km) are based on powers of ten, while imperial units (inch, foot, yard, mile) use varied factors. This tool converts freely between both.
Converts a length or distance between 9 units including metric (mm, cm, m, km) and imperial (inch, foot, yard, mile) plus nautical miles. Click any result tile to use that value as your new input.
All units convert through meters as base unit. Click any tile to use that value as new input.