Length Converter
Convert between metric and imperial length units instantly. Supports meters, feet, inches, centimeters, kilometers, miles, yards, and millimeters with accurate international conversion standards.
Conversion Details
How Length Conversion Works
Value × Conversion Factor = Result
Length conversion works by multiplying your measurement by a conversion factor—a fixed ratio between two units. For example, since 1 meter equals 3.28084 feet, multiplying meters by 3.28084 gives you feet.
The key principle: when converting from a larger unit to a smaller unit (like meters to centimeters), multiply because you'll have more of the smaller units. When converting from a smaller unit to a larger unit (like inches to feet), you're essentially dividing because you'll have fewer of the larger units.
5 meters × 3.28084 (conversion factor) = 16.4042 feet
Where:
- Value: The original measurement (5 meters)
- Conversion Factor: The ratio between units (3.28084 ft/m)
- Result: The converted measurement (16.4042 feet)
Real-World Length Conversion Scenarios
🏗️ Construction Blueprint
- Measurement: Wall length 3.5 meters
- Need: Convert to feet and inches
- Result: 11 feet 5.8 inches
Key Insight: Contractors in the US work with feet and inches, but many blueprints use metric. 3.5 m = 11.4829 ft, which is 11 ft + 0.4829 × 12 = 11 ft 5.8 inches—critical for accurate framing.
✈️ International Flight Distance
- Measurement: 8,500 kilometers
- Need: Convert to miles
- Result: 5,282 miles
Key Insight: Airlines often report distance in kilometers internationally. 8,500 km × 0.621371 = 5,282 miles. A Los Angeles to London flight is roughly this distance—about 10-11 hours.
🏃 Running Track Length
- Measurement: 400-meter track
- Need: Understand in feet
- Result: 1,312.3 feet (quarter mile)
Key Insight: Olympic tracks are 400m (1,312.3 ft), which is why 4 laps equals 1 mile. Converting helps runners understand pace—if you run 400m in 90 seconds, that's a 6-minute mile pace.
🧵 Fabric Purchase
- Measurement: Need 2.5 yards of fabric
- Need: Store sells in meters
- Result: 2.286 meters (round to 2.3m)
Key Insight: US patterns use yards, European stores use meters. 2.5 yd × 0.9144 = 2.286m. Always round up slightly when buying fabric to avoid shortages—ask for 2.3 or 2.5 meters.
Quick Conversion Reference Table
| From | To Meters | To Feet | To Inches | To Centimeters |
|---|---|---|---|---|
| 1 Meter | 1 | 3.28084 | 39.3701 | 100 |
| 1 Foot | 0.3048 | 1 | 12 | 30.48 |
| 1 Inch | 0.0254 | 0.0833 | 1 | 2.54 |
| 1 Kilometer | 1,000 | 3,280.84 | 39,370.1 | 100,000 |
| 1 Mile | 1,609.34 | 5,280 | 63,360 | 160,934 |
| 1 Yard | 0.9144 | 3 | 36 | 91.44 |
Understanding Metric vs Imperial Systems
📏 Metric System (SI)
The metric system uses the meter as the base unit and scales by powers of 10. This makes conversions straightforward—just move the decimal point.
Common Units: kilometer (1,000m), meter (1m), centimeter (0.01m), millimeter (0.001m)
Example: 1 km = 1,000 m = 100,000 cm = 1,000,000 mm. Converting within metric just requires multiplying or dividing by 10, 100, 1,000, etc.
📐 Imperial System (US Customary)
The imperial system uses historical units with varied conversion factors. It's used primarily in the United States, though the UK uses a mix of both systems.
Common Units: mile (5,280 ft), yard (3 ft), foot (12 in), inch (base unit)
Example: 1 mile = 1,760 yards = 5,280 feet = 63,360 inches. Conversions require memorizing specific factors like 12 inches per foot or 5,280 feet per mile.
🌍 Why Two Systems?
The metric system was developed in France in the 1790s based on scientific principles. Most of the world adopted it for its simplicity. The US retained imperial units from its British colonial history.
Global Use: 195 countries use metric as their official system. Only the US, Liberia, and Myanmar primarily use imperial, though the US uses metric in science and military.
Practical Impact: International trade, science, and engineering often require conversions between systems, making converters essential for accurate work.
🔄 The Conversion Factor
The key to converting between metric and imperial is knowing the defined relationships: 1 inch = 2.54 cm exactly (by international agreement), and 1 foot = 0.3048 m exactly.
Example: To convert 10 inches to cm: 10 × 2.54 = 25.4 cm. To go back: 25.4 ÷ 2.54 = 10 inches.
Accuracy: These are defined conversions, not approximations, so they're exact for practical use. Rounding only affects the display of results.
Essential Conversion Factors to Remember
💡 Inches to Centimeters
Factor: 1 inch = 2.54 cm (exactly)
This is THE fundamental conversion between metric and imperial. It's defined by international agreement and is exact, not approximate. Multiply inches by 2.54 to get centimeters; divide centimeters by 2.54 to get inches.
Quick Check: A 12-inch ruler = 30.48 cm (2.54 × 12). A standard sheet of paper (8.5 × 11 inches) = 21.59 × 27.94 cm.
💡 Meters to Feet
Factor: 1 meter ≈ 3.28 feet
For quick mental math, remember that 1 meter is about 3.3 feet. The exact conversion is 3.28084, but 3.28 is close enough for most purposes. This means a 10-meter room is about 33 feet.
Why it works: Since 1 foot = 0.3048 m exactly, the reciprocal (1 ÷ 0.3048) gives us 3.28084 ft/m.
💡 Kilometers to Miles
Factor: 1 km ≈ 0.621 miles (or 1 mile ≈ 1.609 km)
For road distances, knowing that 1 km is about 5/8 of a mile helps. A 100 km drive is about 62 miles. Going the other direction, a 60-mile trip is about 100 km (actually 96.5 km).
Speed conversion: 100 km/h ≈ 62 mph. Highway speed limits make sense once you convert: 80 km/h = 50 mph, 120 km/h = 75 mph.
💡 Yards to Meters
Factor: 1 yard ≈ 0.914 meters (or 1 meter ≈ 1.094 yards)
A yard and a meter are close enough that they're sometimes used interchangeably in casual conversation, though a meter is about 9% longer. A 100-yard football field is 91.44 meters.
Fabric tip: If a pattern calls for 5 yards, you need about 4.6 meters. Always round up when buying fabric!
💡 Feet to Inches
Factor: 1 foot = 12 inches (exactly)
This is pure imperial—12 inches make a foot. When measuring height, 6 feet = 72 inches. When you see 5'10", that's 5 feet + 10 inches = 70 inches total.
Construction use: Building materials are sized in inches: 2×4 lumber (actually 1.5" × 3.5"), 4×8 plywood (48" × 96"), making inch-to-foot conversion essential.
💡 Centimeters to Millimeters
Factor: 1 cm = 10 mm (exactly)
This is metric's beauty—simple powers of 10. Precision work often uses millimeters: a 5mm bolt, 10mm wrench. For visualizing, a dime is about 1.35mm thick, a credit card is about 0.76mm.
Scientific notation: Small measurements like bacteria (micrometers) or light wavelengths (nanometers) follow the same pattern: 1 mm = 1,000 μm = 1,000,000 nm.
⚠️ Common Length Conversion Mistakes to Avoid
Confusing When to Multiply vs Divide
Forgetting the direction of conversion leads to results that are off by factors of 100 or more.
Why It Matters: If you divide when you should multiply (or vice versa), your answer will be drastically wrong. Converting 5 meters to centimeters requires multiplying (5 × 100 = 500 cm), not dividing (5 ÷ 100 = 0.05 cm would be wrong).
What To Do Instead: Remember: larger unit → smaller unit = multiply (you get more). Smaller unit → larger unit = divide (you get fewer). Think logically: should your answer be bigger or smaller than the starting number?
Using Approximate Conversions for Precise Work
Rounding conversion factors too early can accumulate errors in engineering or construction.
Why It Matters: Using "1 meter ≈ 3.3 feet" instead of 3.28084 feet seems minor, but over 100 meters the error is 19 feet! In construction, this could mean walls that don't meet or materials that don't fit.
What To Do Instead: Use exact conversion factors (2.54 cm/inch, 3.28084 ft/m, 1.609344 km/mile) for anything requiring precision. Round only your final answer, not intermediate calculations.
Mixing Unit Systems Within Calculations
Combining meters with feet in formulas without converting causes catastrophic errors.
Why It Matters: NASA's Mars Climate Orbiter was destroyed in 1999 because one team used imperial units while another used metric—a $125 million mistake. Even in everyday math, mixing systems produces meaningless results.
What To Do Instead: Always convert ALL measurements to the same system before calculating. If working in metric, convert all imperial measurements first. If working in imperial, convert all metric measurements first.
Selecting the Wrong Input Unit
Choosing centimeters instead of meters (or vice versa) in the dropdown produces results off by 100×.
Why It Matters: If you have 50 centimeters but select "meters" in the dropdown, the converter calculates as if you have 50 meters—giving you results 100 times too large. This is especially common when source documents are unclear.
What To Do Instead: Double-check your source measurement's unit before selecting. Look for abbreviations: m vs cm, ft vs in, km vs mi. When in doubt, think about whether the number makes sense: is a person's height really 180 meters?
Ignoring Significant Figures
Reporting conversions with false precision (too many decimal places) implies accuracy you don't have.
Why It Matters: If you measure something as "about 5 meters" with a tape measure, reporting the conversion as "16.4042 feet" implies you know it to within 0.0001 feet (0.03 mm)—which you don't. This misleads others about measurement accuracy.
What To Do Instead: Match your result's precision to your input's precision. "About 5 meters" converts to "about 16 feet" or "16.4 feet" at most. Keep 4-5 decimal places only when your original measurement is that precise (like 5.0000 meters).
Confusing Similar-Sounding Units
Mixing up nautical miles with statute miles, or statute miles with kilometers, gives very wrong distances.
Why It Matters: A nautical mile (1.852 km) is 15% longer than a statute mile (1.609 km). Maritime and aviation distances use nautical miles, but road distances use statute miles. Using the wrong one puts you in the wrong location—critical for navigation.
What To Do Instead: Confirm which type of mile you're working with. Nautical miles are used for sea and air (1 nmi = 1.15078 statute mi). When converting, explicitly note which you're using to avoid confusion.
Sources & Methodology
National Institute of Standards and Technology (NIST)
Official US source for measurement standards and conversion factors. We use NIST's exact conversion definitions: 1 inch = 2.54 centimeters exactly (by international agreement).
View Source →International Bureau of Weights and Measures (BIPM)
Global authority on the International System of Units (SI). Provides the scientific definitions for the meter and all metric length units used worldwide.
View Source →International Yard and Pound Agreement (1959)
Historical agreement that standardized imperial units internationally. Defined 1 yard = 0.9144 meter exactly, establishing all imperial-to-metric conversions still used today.
View Source →How to Use This Calculator
- Step 1: Enter your length value in the "Value" field. You can use whole numbers (like 100) or decimals (like 5.5). The calculator accepts any positive or negative number.
- Step 2: Select the unit you're converting FROM in the "From Unit" dropdown. Choose from 12 common units including meters, feet, inches, centimeters, kilometers, miles, yards, and more specialized units like nautical miles or micrometers.
- Step 3: Select the unit you're converting TO in the "To Unit" dropdown. The calculator automatically converts as soon as you make your selection—no need to click a "Calculate" button.
- Step 4: View your result immediately in the purple result box. The conversion happens in real-time as you type, so you can see how changing your input value affects the output.
- Step 5: Check the "Conversion Details" section below the result to see the exact formula and conversion factor used. This helps you understand the math and verify the calculation is correct.
- Step 6: Use the quick reference tables below to verify common conversions or understand relationships between units. The tables show how units relate to each other at a glance.
Common Questions
To convert meters to feet, multiply the number of meters by 3.28084. For example, 5 meters × 3.28084 = 16.4042 feet. This works because 1 meter equals exactly 3.28084 feet in the international system. Our calculator does this automatically—just enter your meters and select "feet" as the target unit.
Metric units (meters, centimeters, kilometers) use a decimal system based on powers of 10, making conversions straightforward. Imperial units (feet, inches, yards, miles) use varied conversion factors like 12 inches per foot or 5,280 feet per mile. The metric system is used worldwide, while imperial is primarily used in the United States. Metric conversions are simpler (just move the decimal), but both systems require knowing specific conversion factors when converting between them.
There are exactly 2.54 centimeters in 1 inch. This is a defined conversion, meaning it's exact rather than approximate—established by international agreement in 1959. To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54. For example: 10 inches = 25.4 cm, and 50 cm = 19.685 inches.
When converting from a larger unit to a smaller unit (like meters to centimeters), multiply because you'll have more of the smaller units. When converting from a smaller unit to a larger unit (like inches to feet), divide because you'll have fewer of the larger units. For example: 5 meters = 500 centimeters (multiply by 100), but 24 inches = 2 feet (divide by 12). Our calculator handles this automatically, but understanding the logic helps you catch errors and estimate conversions mentally.
Online length converters using standard conversion factors are highly accurate for practical purposes. Our converter uses internationally recognized conversion factors (like 1 inch = 2.54 cm exactly) from NIST and BIPM standards. For most everyday applications—construction, travel, shopping—these conversions are precise enough. For scientific work requiring extreme precision, consider the measurement accuracy of your original value as well; our converter maintains full precision internally and only rounds for display.
Yes! A nautical mile equals 1.15078 statute miles or 1.852 kilometers. Nautical miles are used in maritime and aviation contexts because they're based on Earth's circumference (1 nautical mile = 1 minute of latitude). To convert: multiply nautical miles by 1.15078 for regular miles, or by 1.852 for kilometers. For example, 10 nautical miles = 11.5078 statute miles = 18.52 kilometers. Our calculator includes nautical miles in the dropdown menu.
Our calculator supports extreme scales: micrometers (μm) for microscopic measurements, nanometers (nm) for wavelengths of light, and even light-years (ly) for astronomical distances. For very small: 1 mm = 1,000 μm = 1,000,000 nm. For very large: 1 light-year ≈ 9.461 trillion kilometers. Simply select the appropriate unit from the dropdown. The calculator handles scientific notation internally and displays results in the most readable format.
To convert feet to inches, multiply by 12 (since there are 12 inches in 1 foot). For example, 5 feet = 60 inches (5 × 12). To convert inches to feet, divide by 12. For example, 72 inches = 6 feet (72 ÷ 12). When dealing with feet and inches together (like 5'8"), first convert: 5 feet = 60 inches, plus 8 inches = 68 inches total. This is common for measuring height.
Disclaimer: This length converter uses internationally recognized conversion factors from NIST and BIPM standards. While calculations are accurate for practical applications, always verify critical measurements independently. For precision work in construction, engineering, or science, consult relevant professional standards and double-check conversions. This calculator is provided for informational purposes and does not replace professional measurement or engineering services.