About This Tool
Length conversion comes up constantly in construction, engineering, travel, fitness, and everyday measurements. The inch-to-centimeter and mile-to-kilometer conversions alone account for hundreds of thousands of monthly searches. This converter goes beyond a single pair of units by showing every conversion simultaneously. Enter a value in any unit and see its equivalent in all eight other units at once: inches, feet, yards, miles, millimeters, centimeters, meters, kilometers, and nautical miles. A reference table of the most commonly needed conversion factors is included below for quick lookup. Results update in real time as you type, no signup or data storage required. Bookmark this page for instant access whenever you need to convert between metric and imperial length measurements.
How to Use This Length Converter
Enter a numeric value in the input field and select the source unit from the dropdown. The converter immediately displays the equivalent value in all other length units using a grid of result cards.
For example, entering "6" with "Feet" selected shows: 72 inches, 2 yards, 0.001136 miles, 1,828.8 mm, 182.88 cm, 1.8288 meters, 0.001829 km, and 0.000988 nautical miles.
The reference table at the bottom lists the most-searched conversion factors with exact values where applicable. The conversions between imperial and metric are based on the internationally agreed definition: 1 inch = 2.54 centimeters exactly.
Key Conversion Factors to Know
Memorizing a few anchor conversions lets you estimate any length conversion mentally:
- 1 inch = 2.54 cm (exact): This is the foundational definition linking imperial and metric length. All other imperial-to-metric length conversions derive from this.
- 1 foot = 12 inches = 30.48 cm: Since 1 foot = 12 inches and 1 inch = 2.54 cm, 1 foot = 12 x 2.54 = 30.48 cm exactly.
- 1 mile = 1.609344 km: A mile equals exactly 5,280 feet. Multiplied by 0.3048 m/ft gives 1,609.344 meters = 1.609344 km.
- 1 meter = 3.28084 feet: Roughly 3 feet 3.4 inches. Useful for quickly estimating room dimensions when reading metric floor plans.
- 1 km = 0.621371 miles: Roughly 5/8 of a mile. When driving in metric countries, multiply km by 0.6 for a rough miles estimate.
- 1 nautical mile = 1.852 km: Defined as one minute of latitude. Used in aviation and maritime navigation worldwide.
Imperial vs. Metric Length Units
The imperial system uses inches, feet, yards, and miles with non-uniform ratios: 12 inches per foot, 3 feet per yard, and 1,760 yards per mile. This makes mental arithmetic difficult for large conversions.
The metric system uses millimeters, centimeters, meters, and kilometers, all related by powers of 10. Moving between units means shifting the decimal point: 1 meter = 100 centimeters = 1,000 millimeters. This simplicity is why the metric system dominates in science and international trade.
In practice, most countries use metric for all purposes. The US, Liberia, and Myanmar are the only nations that have not officially adopted the metric system for everyday use, though US science and military applications use metric units. Many American products now list both measurement systems on packaging.
One common source of confusion is the difference between a statute mile (the standard US mile at 5,280 feet) and a nautical mile (1,852 meters). Nautical miles are used exclusively in aviation and maritime contexts. A speed of 1 nautical mile per hour is called 1 knot.
Practical Applications of Length Conversion
Length conversions appear in many daily and professional scenarios:
- Construction: US blueprints use feet and inches, but many materials (plywood, tile) are manufactured to metric specifications. A 4x8 sheet of plywood is 1,219 mm x 2,438 mm.
- Fitness and Health: Treadmills may display distance in miles or kilometers. Marathon distance is 42.195 km (26.219 miles). Track events use meters (100m, 400m, 1500m).
- Travel: Speed limits, road signs, and GPS directions use kilometers in most countries. A 100 km/h speed limit equals about 62 mph.
- Science: Measurements at small scales use millimeters or micrometers. At large scales, astronomers use kilometers, astronomical units, or light-years.
- Shopping online: Product dimensions from international sellers are often in centimeters. Knowing that 30 cm is roughly 1 foot helps gauge whether furniture or clothing will fit.
Frequently Asked Questions
How many centimeters are in an inch?
Exactly 2.54 centimeters. This is not an approximation. The international inch was defined in 1959 as exactly 25.4 millimeters, which makes 1 inch = 2.54 cm a precise, exact conversion. All other imperial-to-metric length conversions build on this definition.
How do I quickly estimate miles to kilometers?
Multiply miles by 1.6 for a close approximation. For even quicker mental math, multiply by 8 and divide by 5. Example: 30 miles x 8 / 5 = 240 / 5 = 48 km (actual: 48.28 km). Another trick: the Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, 21...) approximates mile-to-km conversions because the ratio between consecutive Fibonacci numbers approaches 1.618, which is close to 1.609.
What is the difference between a nautical mile and a regular mile?
A regular (statute) mile is 5,280 feet or 1,609.344 meters. A nautical mile is 1,852 meters (about 6,076 feet), making it roughly 15% longer than a statute mile. The nautical mile was defined based on the circumference of the Earth: it equals one minute of latitude, which makes navigation calculations simpler. Sailors and pilots use nautical miles and knots (nautical miles per hour) as their standard units.
How tall is 6 feet in centimeters?
6 feet equals exactly 182.88 centimeters. To calculate: 6 feet x 30.48 cm/foot = 182.88 cm. In most metric countries, this height is typically expressed as 183 cm or 1.83 meters. For height conversions, remember that 5 feet = 152.4 cm and each additional inch adds 2.54 cm.
Why is a yard almost the same as a meter?
A yard (0.9144 meters) and a meter are close in size but developed independently. The yard has English origins, historically defined as the distance from the nose to the tip of the outstretched arm of King Henry I. The meter was defined during the French Revolution as one ten-millionth of the distance from the equator to the North Pole. The 8.56% difference between them is coincidental. For rough estimates, treating 1 yard as 1 meter is close enough, but for precision work the 0.0856 meter difference adds up quickly.