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Length Unit Converter — Metric, Imperial & More

Convert between 16 length units instantly — metric, imperial, nautical & astronomical. 1 inch = 2.54 cm. Free, private, runs in your browser.

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Result
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Reviewed for SI compliance and conversion factor accuracy — Go Tools Engineering Team · Mar 22, 2026

Quick Reference

How Many Centimeters in an Inch?

1 inch = 2.54 cm (exact) This is the internationally defined exact conversion factor, established by the 1959 yard and pound agreement. To convert inches to centimeters, multiply by 2.54. For example, 12 inches = 30.48 cm.

How Many Feet in a Meter?

1 meter = 3.28084 feet Conversely, 1 foot equals exactly 0.3048 meters. To convert meters to feet, multiply by 3.28084. A 6-foot person is about 1.83 meters tall.

How Many Kilometers in a Mile?

1 mile = 1.609344 km (exact) To convert miles to kilometers, multiply by 1.609344. For quick mental math, multiply miles by 1.6. A marathon (26.2 miles) is approximately 42.2 km.

What Is a Length Unit Converter?

A length unit converter is a tool that translates distance and length measurements between different units of measure — bridging the metric system (meter, kilometer, centimeter) and the imperial system (inch, foot, yard, mile), as well as specialized units used in science, navigation, and astronomy.

The metric system, used by most of the world, is decimal-based: each unit differs from the next by a power of 10. The core unit is the meter, officially defined since 2019 by the International Bureau of Weights and Measures (BIPM) in the International System of Units (SI) as the distance light travels in a vacuum in exactly 1/299,792,458 of a second — anchoring the meter to a universal physical constant rather than any physical artifact. Prefixes like kilo- (1,000), centi- (0.01), milli- (0.001), micro- (0.000001), and nano- (0.000000001) scale the meter up or down. The imperial system, still common in the United States, uses inches, feet (12 inches), yards (3 feet), and miles (5,280 feet).

Beyond everyday units, this converter supports nautical miles (used in aviation and maritime navigation), and astronomical units like the light year (9.461 trillion km), the astronomical unit (Earth-Sun distance, ~149.6 million km), and the parsec (~3.26 light years). It also includes the fathom (6 feet, used for water depth) and the furlong (220 yards, used in horse racing).

All conversions use the internationally defined exact factors established by the 1959 international yard and pound agreement, as published by BIPM and NIST, ensuring precise results traceable to the SI definition of the meter. Processing runs entirely in your browser — no data is transmitted to any server, so your measurements stay completely private.

Need to convert other measurement types? Try our weight converter for mass units, volume converter for liquid measurements, or temperature converter for Celsius, Fahrenheit, and Kelvin.

// Key conversion factors (exact):
// 1 inch  = 2.54 cm
// 1 foot  = 0.3048 m
// 1 yard  = 0.9144 m
// 1 mile  = 1.609344 km

// JavaScript conversion examples:
const inchesToCm = (inches) => inches * 2.54;
const feetToMeters = (feet) => feet * 0.3048;
const milesToKm = (miles) => miles * 1.609344;
const kmToMiles = (km) => km / 1.609344;

console.log(inchesToCm(12));    // 30.48
console.log(feetToMeters(6));   // 1.8288
console.log(milesToKm(26.2));   // 42.164928

Key Features of This Length Converter

16 Length Units Supported

Convert between kilometer, meter, centimeter, millimeter, micrometer, nanometer, mile, yard, foot, inch, nautical mile, light year, astronomical unit, parsec, fathom, and furlong.

Instant Real-Time Conversion

Results update as you type — no need to click a convert button. Change units and see the result immediately.

One-Click Swap

Reverse the conversion direction instantly with the swap button, without re-entering your value.

Precise Exact Factors

Uses internationally defined exact conversion factors (1 inch = 2.54 cm, 1 mile = 1,609.344 m) for maximum accuracy.

Metric, Imperial & Astronomical

Covers everyday units like feet and meters, plus specialized units like nautical miles, light years, parsecs, and astronomical units.

100% Browser-Based & Private

All calculations happen locally in your browser. No server requests, no tracking, no data storage — your values never leave your device.

Length Conversion Examples

Inches to Centimeters — Screen Size

27
68.58 cm

A 27-inch monitor diagonal equals 68.58 centimeters. The conversion factor is 1 inch = 2.54 cm exactly, established by international agreement in 1959.

Feet to Meters — Room Height

8
2.4384 m

A standard 8-foot ceiling is approximately 2.44 meters. This conversion is essential for construction and interior design when working across metric and imperial systems.

Miles to Kilometers — Road Distance

26.2
42.1648 km

A marathon distance of 26.2 miles equals approximately 42.16 kilometers. The conversion factor is 1 mile = 1.609344 km exactly.

Meters to Feet — Athletic Field

100
328.0840 ft

A 100-meter sprint track equals about 328 feet. Track and field events often require converting between metric (official) and imperial measurements.

Kilometers to Miles — Driving Distance

500
310.6856 mi

A 500 km road trip is approximately 311 miles. Useful when traveling between countries that use different measurement systems.

Light Years to Kilometers — Astronomical Distance

4.24
4.0114 × 10¹³ km

Proxima Centauri, the nearest star to our Sun, is about 4.24 light years away — roughly 40 trillion kilometers. One light year equals 9.461 trillion km.

How to Convert Common Length Units

Quick reference for the most popular length unit conversions between metric and imperial systems.

How to Convert Inches to Centimeters

Inch (in) → Centimeter (cm)

Multiply the number of inches by 2.54 to get centimeters. This is an exact conversion factor defined by international agreement. For example, 12 inches = 30.48 cm. This conversion is commonly needed for screen sizes, paper dimensions, and clothing measurements.

12 in → 30.48 cm

For quick mental math, multiply inches by 2.5 for an approximate result — it is only 1.6% off from the exact factor of 2.54.

Try it above — enter your value and see the result instantly.

How to Convert Feet to Meters

Foot (ft) → Meter (m)

Multiply the number of feet by 0.3048 to get meters. This is an exact conversion factor. For example, 6 feet = 1.8288 meters. This conversion is frequently used for height, room dimensions, and elevation measurements.

6 ft → 1.8288 m

A quick approximation: divide feet by 3.3 to get meters. For height, remember that 5 feet is about 1.52 m and 6 feet is about 1.83 m.

Try it above — enter your value and see the result instantly.

How to Convert Miles to Kilometers

Mile (mi) → Kilometer (km)

Multiply the number of miles by 1.609344 to get kilometers. For example, 10 miles = 16.09344 km. This conversion is essential for road distances, running events, and international travel between countries using different systems.

10 mi → 16.0934 km

For a quick estimate, multiply miles by 1.6. Fun fact: the Fibonacci sequence approximates mile-to-km conversion — 5 miles is about 8 km, 8 miles is about 13 km.

Try it above — enter your value and see the result instantly.

How to Convert Centimeters to Inches

Centimeter (cm) → Inch (in)

Divide the number of centimeters by 2.54 to get inches. For example, 30 cm = 11.811 inches. This reverse conversion is useful when shopping for products sized in metric units or interpreting international specifications.

30 cm → 11.811 in

For a quick estimate, divide centimeters by 2.5 — this gives a result that is only about 1.6% higher than the exact value.

Try it above — enter your value and see the result instantly.

How to Convert Meters to Feet

Meter (m) → Foot (ft)

Divide the number of meters by 0.3048, or equivalently multiply by 3.28084, to get feet. For example, 2 meters = 6.5617 feet. This is commonly needed for height conversions, real estate listings, and construction measurements.

2 m → 6.5617 ft

A quick approximation: multiply meters by 3.3 to get feet. Remember that 1 meter is just over 3 feet 3 inches.

Try it above — enter your value and see the result instantly.

How to Convert Kilometers to Miles

Kilometer (km) → Mile (mi)

Divide the number of kilometers by 1.609344, or equivalently multiply by 0.621371, to get miles. For example, 100 km = 62.137 miles. Essential for interpreting road signs and speed limits when traveling internationally.

100 km → 62.137 mi

For a quick estimate, multiply kilometers by 0.6. Or use the Fibonacci trick in reverse: 13 km is about 8 miles, 8 km is about 5 miles.

Try it above — enter your value and see the result instantly.

Length Conversion Charts

Pre-calculated reference tables for the most common length conversions. Bookmark this page for quick lookups.

Inches to Centimeters Chart

Inches to centimeters conversion table (1-100 in)
IN CM
1 2.54
2 5.08
3 7.62
4 10.16
5 12.7
6 15.24
7 17.78
8 20.32
9 22.86
10 25.4
11 27.94
12 30.48
13 33.02
14 35.56
15 38.1
16 40.64
17 43.18
18 45.72
19 48.26
20 50.8
25 63.5
30 76.2
35 88.9
40 101.6
45 114.3
50 127
55 139.7
60 152.4
65 165.1
70 177.8
75 190.5
80 203.2
85 215.9
90 228.6
95 241.3
100 254

Feet to Meters Chart

Feet to meters conversion table (1-100 ft)
FT M
1 0.3048
2 0.6096
3 0.9144
4 1.2192
5 1.524
6 1.8288
7 2.1336
8 2.4384
9 2.7432
10 3.048
11 3.3528
12 3.6576
13 3.9624
14 4.2672
15 4.572
16 4.8768
17 5.1816
18 5.4864
19 5.7912
20 6.096
25 7.62
30 9.144
35 10.668
40 12.192
45 13.716
50 15.24
55 16.764
60 18.288
65 19.812
70 21.336
75 22.86
80 24.384
85 25.908
90 27.432
95 28.956
100 30.48

Miles to Kilometers Chart

Miles to kilometers conversion table (1-100 mi)
MI KM
1 1.609344
2 3.218688
3 4.828032
4 6.437376
5 8.04672
6 9.656064
7 11.265408
8 12.874752
9 14.484096
10 16.09344
11 17.702784
12 19.312128
13 20.921472
14 22.530816
15 24.14016
16 25.749504
17 27.358848
18 28.968192
19 30.577536
20 32.18688
25 40.2336
30 48.28032
35 56.32704
40 64.37376
45 72.42048
50 80.4672
55 88.51392
60 96.56064
65 104.60736
70 112.65408
75 120.7008
80 128.74752
85 136.79424
90 144.84096
95 152.88768
100 160.9344

How to Use the Length Converter

  1. 1

    Enter a Value

    Type or paste a numeric value into the input field. The tool accepts integers and decimal numbers of any size.

  2. 2

    Select the Source Unit

    Choose the unit you are converting from using the 'From' dropdown. Options include metric (km, m, cm, mm, um, nm), imperial (mi, yd, ft, in), nautical, and astronomical units.

  3. 3

    Select the Target Unit

    Choose the unit you want to convert to using the 'To' dropdown. The result updates instantly as you change either unit.

  4. 4

    Copy or Swap

    Click the copy button to copy the result to your clipboard. Use the swap button to reverse the conversion direction instantly.

Use Cases for Length Conversion

Travel & Navigation
Convert road distances between kilometers and miles when traveling between countries with different measurement systems.
Construction & Home Improvement
Convert architectural measurements between feet/inches and meters/centimeters for international building standards and material specifications.
Science & Engineering
Convert between metric scales (nm, um, mm, m, km) for laboratory measurements, manufacturing tolerances, and engineering specifications.
Health & Fitness
Convert height between feet/inches and centimeters, or running distances between miles and kilometers for international race events.
Astronomy & Space Science
Convert between light years, astronomical units, parsecs, and kilometers for understanding cosmic distances and celestial mechanics.
Maritime & Aviation
Convert nautical miles to kilometers or statute miles for flight planning, marine navigation, and chart reading.

Technical Details

Exact Conversion Factors
Based on the 1959 international yard and pound agreement: 1 yard = 0.9144 m exactly, from which 1 inch = 25.4 mm and 1 mile = 1,609.344 m are derived.
Double-Precision Arithmetic
Uses IEEE 754 double-precision floating-point numbers, providing at least 15 significant digits of precision for all conversions.
Client-Side Processing
All conversion logic runs in JavaScript within your browser. Zero network calls are made — the tool works fully offline once loaded.

Best Practices for Length Conversion

Use Exact Factors for Critical Work
For engineering and scientific work, use the exact conversion factors (e.g., 1 inch = 25.4 mm exactly) rather than rounded approximations.
Match Precision to Your Measurement
A ruler measured to the nearest millimeter does not justify reporting a conversion to 10 decimal places. Round your result to match the precision of your original measurement.
Double-Check Unit Systems in Context
The Mars Climate Orbiter was lost due to a metric-imperial unit mismatch. Always verify which unit system your collaborators expect.

Length Conversion FAQ

How many centimeters are in an inch?
There are exactly 2.54 centimeters in one inch. This is not an approximation — it is the exact conversion factor defined by the international yard and pound agreement of 1959. To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54. For example, 12 inches = 30.48 cm, and 10 cm = 3.937 inches.
How many feet are in a meter?
One meter equals approximately 3.28084 feet, or more precisely, 1 meter = 3.2808398950131 feet. Conversely, 1 foot = 0.3048 meters exactly. This means a 6-foot person is about 1.8288 meters tall. To convert meters to feet, multiply by 3.28084. To convert feet to meters, multiply by 0.3048.
What is the formula to convert inches to cm?
To convert inches to centimeters, multiply the inch value by 2.54. The formula is: cm = inches × 2.54. This is an exact conversion factor defined by international agreement in 1959. For example, 6 inches = 6 × 2.54 = 15.24 cm. To convert back from cm to inches, divide by 2.54: inches = cm ÷ 2.54.
What is a nautical mile and how does it differ from a regular mile?
A nautical mile equals exactly 1,852 meters (about 1.151 regular miles or 6,076 feet). It was originally defined as one minute of arc along a meridian of the Earth, making it naturally suited for navigation. A regular (statute) mile equals 1,609.344 meters or 5,280 feet. Nautical miles are used in aviation and maritime navigation because they relate directly to degrees of latitude: 60 nautical miles = 1 degree of latitude.
Which countries still use the imperial system?
Only three countries primarily use the imperial system for everyday measurements: the United States, Myanmar (Burma), and Liberia. The UK uses a mix — road distances are in miles, but most other measurements are metric. Canada officially uses metric but commonly uses feet and inches for personal height and real estate. Most scientific, medical, and international trade contexts use the metric system worldwide.
How tall is 5'7 in cm?
5 feet 7 inches equals 170.18 centimeters. To calculate: convert feet to inches (5 × 12 = 60), add remaining inches (60 + 7 = 67 total inches), multiply by 2.54 (67 × 2.54 = 170.18 cm). Common heights: 5'0" = 152.4 cm, 5'5" = 165.1 cm, 5'7" = 170.18 cm, 5'10" = 177.8 cm, 6'0" = 182.88 cm, 6'2" = 187.96 cm.
What is a light year and how far is it?
A light year is the distance that light travels in one year in a vacuum — approximately 9.461 trillion kilometers (9.461 × 10¹² km) or about 5.879 trillion miles. Despite the name, a light year is a unit of distance, not time. For perspective, light from the Sun takes about 8 minutes to reach Earth (1 AU = 149.6 million km), while the nearest star system, Alpha Centauri, is about 4.37 light years away. Light years are used to express distances between stars and galaxies because using kilometers would require unwieldy numbers.
How accurate is this length converter?
This converter uses the internationally defined exact conversion factors: 1 inch = 25.4 mm exactly, 1 yard = 0.9144 m exactly, and 1 mile = 1,609.344 m exactly. All calculations use IEEE 754 double-precision floating-point arithmetic, providing at least 15 significant digits of precision. For everyday conversions, the results are more accurate than any physical measurement. The only limitation is the inherent rounding of floating-point numbers at extreme precision, which affects digits beyond the 15th significant figure.
How do metric prefixes work for length units?
Metric length units are based on the meter, with prefixes indicating powers of 10. Common prefixes from large to small: kilo (km) = 1,000 m, no prefix (m) = 1 m, centi (cm) = 0.01 m, milli (mm) = 0.001 m, micro (um) = 0.000001 m, and nano (nm) = 0.000000001 m. Each step between adjacent common prefixes is a factor of 1,000 (except centi, which is 1/100 of a meter). This decimal-based system makes metric conversions straightforward: moving the decimal point is all that is required.
Is my data safe when using this length converter?
Yes, completely. All conversions are performed locally in your browser using JavaScript. No data is sent to any server — there are no network requests, no cookies, and no analytics on your input. The conversion logic runs entirely on your device, meaning your values never leave your browser. You can verify this by disconnecting from the internet and using the tool — it works fully offline once the page has loaded.
How many feet are in a mile?
There are exactly 5,280 feet in one mile. This relationship is defined by the statute mile, the standard mile used in the United States and United Kingdom. Other useful conversions: 1 mile = 1,760 yards = 63,360 inches = 1,609.344 meters = 1.609344 kilometers. The word 'mile' derives from the Latin 'mille passus' meaning one thousand paces.
What is the SI unit of length?
The meter (m) is the SI (International System of Units) base unit of length. Since 2019, it is defined as the distance light travels in a vacuum in exactly 1/299,792,458 of a second. All other metric length units are derived from the meter using decimal prefixes: 1 kilometer = 1,000 meters, 1 centimeter = 0.01 meters, 1 millimeter = 0.001 meters, 1 micrometer = 0.000001 meters, 1 nanometer = 0.000000001 meters.
I need to convert my height from feet to centimeters for a medical form — how do I do it?
First, convert your total height to inches: multiply the feet by 12 and add any remaining inches. For example, 5 feet 9 inches = (5 x 12) + 9 = 69 inches. Then multiply by 2.54 to get centimeters: 69 x 2.54 = 175.26 cm. You can enter 69 in this tool with inches as the source unit and centimeters as the target to get the exact result. Common heights for reference: 5'4" = 162.6 cm, 5'7" = 170.2 cm, 5'10" = 177.8 cm, 6'1" = 185.4 cm. Medical forms worldwide use centimeters, so this conversion comes up frequently for travelers and expats.
I need to convert kilometers to miles for a US road trip — what is the quickest way?
Multiply kilometers by 0.621 for a quick estimate, or use this tool for exact results. For mental math on the road, a handy trick is the Fibonacci approximation: consecutive Fibonacci numbers approximate the km-to-miles ratio. So 8 km is about 5 miles, 13 km is about 8 miles, 21 km is about 13 miles. For speed limits, 100 km/h is about 62 mph, 120 km/h is about 75 mph, and 130 km/h is about 81 mph. Enter any distance in this tool to get the precise conversion instantly.
I need to figure out if my furniture will fit through a doorway — how do I convert between inches and centimeters?
Multiply inches by 2.54 to get centimeters, or divide centimeters by 2.54 to get inches. A standard US interior doorway is 80 inches (203 cm) tall and 30-36 inches (76-91 cm) wide. If your furniture is measured in centimeters (common for IKEA and European brands), divide by 2.54 to compare with your doorway in inches. For example, a 200 cm tall bookshelf is 78.7 inches — it will fit through a standard door with about 1.3 inches to spare. Always measure the diagonal of the item if you need to tilt it to fit through.

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