Length Converter
Convert between different units of length and distance.
Quick Examples
Length Conversions
Common Conversion Factors
1 foot = 0.3048 m
1 mile = 1.60934 km
1 nautical mile = 1.852 km
Metric Prefixes
| Prefix | Symbol | Multiplier |
|---|---|---|
| kilo | k | 1000 |
| centi | c | 0.01 |
| milli | m | 0.001 |
| micro | μ | 0.000001 |
| nano | n | 0.000000001 |
Everyday Comparisons
- 5 km ≈ 3.1 miles
- 100 m ≈ 328 feet
- Marathon: 42.195 km ≈ 26.2 miles
- 1 light year ≈ 9.461 trillion km
How Length Conversion Works
Rather than memorizing a separate formula for every pair of units, conversions run through a single base unit — the meter. Convert the starting value into meters, then convert that meter value into the target unit:
result = value in meters ÷ (meters per target unit)
This two-step method needs only one factor per unit. The calculator above uses the exact international definitions: 1 inch = 0.0254 m, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1,609.344 m, and 1 nautical mile = 1,852 m.
Metric vs Imperial
The metric system scales in powers of ten from the meter — a kilometer is 1,000 meters, a centimeter is one hundredth — so conversion within it is a matter of moving the decimal point. Imperial units come from historical body-based and agricultural measures, which is why they use irregular factors: 12 inches to a foot, 3 feet to a yard, 1,760 yards to a mile.
Worked Examples
Example 1: Feet to Meters
Convert 5 feet to meters: 5 × 0.3048 = 1.524 m. Checking the other direction: 1.524 ÷ 0.3048 = 5 feet.
Example 2: Kilometers to Miles
Convert 10 kilometers to miles: 10 × 1,000 = 10,000 meters; 10,000 ÷ 1,609.344 ≈ 6.2137 miles.
Example 3: Height in Feet and Inches
A person is 175 cm tall — what is that in feet and inches? 175 ÷ 30.48 = 5.7415 ft, so 5 full feet plus 0.7415 × 12 = 8.9 inches: 5 ft 8.9 in. This mixed-unit output is the standard format for human height in the US and UK.
Height Conversion Quick Chart
| ft/in | cm | ft/in | cm |
|---|---|---|---|
| 4'10" | 147.3 | 5'10" | 177.8 |
| 5'4" | 162.6 | 6'4" | 193.0 |
| 5'7" | 170.2 | 6'6" | 198.1 |
Conversions Worth Memorizing
| Conversion | Factor | Exact? |
|---|---|---|
| 1 inch = ? cm | 2.54 | Exact |
| 1 foot = ? m | 0.3048 | Exact |
| 1 yard = ? m | 0.9144 | Exact |
| 1 mile = ? km | 1.609344 | Exact |
| 1 meter = ? ft | 3.28084 | Approximate |
| 1 km = ? miles | 0.621371 | Approximate |
| 1 nautical mile = ? m | 1,852 | Exact |
Nautical Miles
The nautical mile is not arbitrary: it was defined as one minute of arc of latitude along a meridian, which ties it directly to Earth's geometry — a degree of latitude is 60 nautical miles anywhere on the globe. It is now fixed at exactly 1,852 meters, and the knot (one nautical mile per hour) remains the standard speed unit in aviation and at sea.
Where Length Conversion Is Used
- Construction: plans drawn in metric countries but lumber and tools marked in feet and inches.
- Manufacturing and machining: a part designed in inches must be cut on a machine calibrated in millimeters — a rounding mistake can make it fail to fit.
- Shipping: carriers calculate cost from package dimensions, which must be expressed in the carrier's units.
- Running and cycling: GPS watches measure in kilometers while race distances are often given in miles (a marathon is 26.2 miles = 42.195 km).
- Shopping: furniture dimensions in centimeters versus inches, clothing sizes across countries.
Common Mistakes
- Converting in the wrong direction: if converting meters to feet produces a smaller number, the factor was applied backwards — meters to feet should grow the number (× 3.28).
- Confusing nautical and statute miles: a nautical mile is 1.852 km; a statute mile is 1.609 km. They differ by about 15%.
- Rounding too early: carry full precision through chained conversions and round only the displayed result.
- Assuming metric–imperial pairs are round numbers: the meter and foot were defined independently, so conversions rarely come out even — a 10-foot wall is 3.048 meters, not 3.