Inch Converter - Convert Inches to Any Length Unit
Enter any length and pick the unit you are converting from, then read off the results in every other unit simultaneously. The converter handles metric (mm, cm, m, km, micrometers, nanometers) and imperial or US units (feet, yards, miles, nautical miles). Results update as you type and the "Show your work" panel shows the exact multiplication step used.
How the inch is defined
The international inch was standardized in 1959 by agreement among English-speaking countries. It is defined as exactly 25.4 millimeters, or equivalently, 1/12 of a foot and 1/36 of a yard. Because the definition is exact, every metric conversion of an inch is also exact - there is no approximation involved. The name comes from the Latin uncia, meaning "one-twelfth part," the same root as ounce. Historically, the inch was linked to the width of a human thumb and varied slightly by country until the 1959 international agreement locked it to the metric system.
How to use this inch converter
Enter your measurement in the "Length" field, then use the "Convert from" dropdown to choose the unit you are starting with. The calculator instantly converts that value to all supported units: millimeters, centimeters, meters, kilometers, feet, yards, miles, nautical miles, micrometers, and nanometers. You can convert in any direction - the tool is not limited to converting from inches outward. For example, enter 30 centimeters and select "Centimeters" to find out how many inches, feet, and millimeters that equals. The "Show your work" panel below the results walks through the exact multiplication factor used for each conversion.
Inches to metric: the key formulas
All metric conversions follow directly from the exact definition 1 in = 25.4 mm. Multiplying or dividing by powers of 10 gives the other metric units: 1 in = 25.4 mm = 2.54 cm = 0.0254 m = 0.0000254 km. For large engineering or astronomy distances, 1 in = 25,400 micrometers and 1 in = 25,400,000 nanometers. Going the other way: 1 cm = 0.3937 in, 1 m = 39.3701 in, and 1 mm = 0.03937 in.
Inches to imperial: feet, yards, and miles
Within the imperial system, the inch is the base unit: 12 inches make 1 foot, 3 feet (36 inches) make 1 yard, and 5,280 feet (63,360 inches) make 1 mile. For everyday construction and craft use, the most common conversion is between inches and feet, often expressed as a mixed number such as 5 ft 6 in. Nautical miles are used in aviation and maritime navigation: one nautical mile equals exactly 1,852 meters, which works out to about 72,913.4 inches.
Quick inch conversion reference
| Inches | Millimeters | Centimeters | Feet | Meters |
|---|---|---|---|---|
| 0.25 (1/4) | 6.35 | 0.635 | 0.0208 | 0.00635 |
| 0.5 (1/2) | 12.7 | 1.27 | 0.0417 | 0.0127 |
| 1 | 25.4 | 2.54 | 0.0833 | 0.0254 |
| 2 | 50.8 | 5.08 | 0.1667 | 0.0508 |
| 3 | 76.2 | 7.62 | 0.25 | 0.0762 |
| 6 | 152.4 | 15.24 | 0.5 | 0.1524 |
| 12 (1 ft) | 304.8 | 30.48 | 1 | 0.3048 |
| 24 (2 ft) | 609.6 | 60.96 | 2 | 0.6096 |
| 36 (1 yd) | 914.4 | 91.44 | 3 | 0.9144 |
| 63,360 (1 mi) | 1,609,344 | 160,934.4 | 5,280 | 1,609.344 |
Common inch values and their exact metric and imperial equivalents.
Frequently asked questions
How many millimeters are in an inch?
Exactly 25.4 millimeters. The international inch has been defined as 25.4 mm since 1959, so this conversion is not an approximation - it is exact. To convert any number of inches to millimeters, multiply by 25.4. To go the other way, divide by 25.4.
How many centimeters are in an inch?
2.54 centimeters exactly. Because 1 cm = 10 mm and 1 in = 25.4 mm, dividing gives 1 in = 2.54 cm. This is probably the most commonly memorized length conversion.
How do I convert inches to feet?
Divide the number of inches by 12. For example, 18 inches divided by 12 = 1.5 feet, or equivalently 1 foot 6 inches. To express the leftover fraction as whole inches, take the decimal part and multiply by 12: 0.5 x 12 = 6 inches.
How do I convert fractional inches like 3/8 inch to metric?
Divide the numerator by the denominator to get a decimal, then multiply by 2.54 to reach centimeters or by 25.4 to reach millimeters. For 3/8 inch: 3 divided by 8 = 0.375, then 0.375 x 25.4 = 9.525 mm exactly.
How many inches are in a meter?
Approximately 39.3701 inches, or exactly 10,000/254 inches. Since 1 in = 0.0254 m, dividing 1 by 0.0254 gives 39.3701... The rounded rule of thumb is "about 39.37 inches per meter."
What is a nautical mile in inches?
One nautical mile equals 1,852 meters. Dividing by 0.0254 m/in gives 72,913.386... inches per nautical mile, or about 72,913.4 inches. Nautical miles are used in maritime and aviation navigation because one nautical mile equals one minute of arc of latitude on the Earth's surface.
How do I convert centimeters to inches without a calculator?
Multiply centimeters by 0.3937. A quick mental shortcut is to divide by 2.54. For example, 10 cm divided by 2.54 is approximately 3.94 inches. Another rough rule: divide centimeters by 2.5 for a fast estimate (giving 4 inches for 10 cm), though that overstates the result by about 2.4 percent.