Length converter
Convert between millimetres, centimetres, metres, kilometres, inches, feet, yards, and miles. Edit any value and all units update simultaneously.
What is the Length Converter?
The length converter handles every common length unit in one place — centimeters, meters, kilometers, inches, feet, yards, and miles — plus less common ones like nautical miles, light-years, and parsecs. Use cm to inches for clothing and screen sizes, meters to feet for heights and building dimensions, km to miles for travel and running distances, and mm to inches for hardware and manufacturing specs. Edit either side and the other updates instantly — no "convert" button.
Centimeters to inches
One centimeter equals 0.3937 inches, and one inch equals exactly 2.54 centimeters. This is the most-searched length conversion because clothing, furniture, and screen sizes are often listed in inches in some markets and centimeters in others.
| cm | Inches | Feet + inches |
|---|---|---|
| 1 cm | 0.3937 in | — |
| 10 cm | 3.937 in | — |
| 30 cm | 11.811 in | — |
| 100 cm | 39.3701 in | 3 ft 3.37 in |
| 170 cm | 66.9291 in | 5 ft 6.93 in |
| 180 cm | 70.8661 in | 5 ft 10.87 in |
Meters to feet
One meter equals 3.2808 feet, and one foot equals exactly 0.3048 meters. This conversion comes up in architecture, building heights, pool lengths, and anywhere dimensions need to be communicated across the metric and imperial systems.
| m | Feet | Yards |
|---|---|---|
| 1 m | 3.2808 ft | 1.0936 yd |
| 5 m | 16.4042 ft | 5.4681 yd |
| 10 m | 32.8084 ft | 10.9361 yd |
| 25 m | 82.021 ft | 27.3403 yd |
| 50 m | 164.042 ft | 54.6807 yd |
| 100 m | 328.084 ft | 109.3613 yd |
Kilometers to miles
One kilometer equals 0.6214 miles, and one mile equals exactly 1.60934 kilometers. Most conversions used for travel distances, speed limits, and running events — a 5K run is 3.1 miles, a marathon is 26.2 miles or 42.2 km.
| km | Miles | Context |
|---|---|---|
| 1 km | 0.6214 mi | Short walk |
| 5 km | 3.1069 mi | 5K run |
| 10 km | 6.2137 mi | 10K run |
| 21.1 km | 13.1109 mi | Half marathon |
| 42.2 km | 26.2219 mi | Marathon |
| 100 km | 62.1371 mi | Long drive |
Millimeters to inches
One millimeter equals 0.0394 inches. This conversion matters most for hardware: screws, drill bits, hex keys, and camera lens filters. Outside the US, most screw specs are in millimeters; US tool catalogs use fractional inches. For quick reference: 3 mm is roughly 1/8 inch, 6 mm is roughly 1/4 inch, 25 mm is just under 1 inch.
How does length conversion work?
Every unit is defined relative to the meter, the SI base unit of length. To convert between any two units, the calculator multiplies by the source unit's meter factor and divides by the target unit's meter factor. The inch-to-meter ratio (0.0254) was fixed by the international yard and pound agreement of 1959. Because the ratios are exact SI-defined constants, the conversions are precise rather than approximate.
Common Uses
- Construction and renovation: Convert between feet/inches and metres when working with imported materials, architect drawings, or international suppliers.
- Online shopping: Convert clothing, shoe, or furniture dimensions between US/UK imperial measurements and metric equivalents before purchasing.
- DIY and home projects: Convert measurements from YouTube tutorials or foreign instruction manuals that use different unit systems than your tools.
- Science and engineering: Convert between SI units (nanometres, micrometres, kilometres) for laboratory calculations, engineering drawings, or academic reports.
- Travel distance planning: Convert mileage or kilometre distances from maps and navigation apps to match the units you think in.
- Sports performance tracking: Convert sprint distances (100 yards to metres), marathon distances, or pool lengths for cross-border event comparisons.
- Textile and fabric measurement: Convert between yards, metres, and centimetres when purchasing fabric from international suppliers or following foreign patterns.
- Real estate comparison: Convert property floor areas between square feet and square metres when comparing listings from different countries.
FAQ
How tall is 170 cm in feet and inches?
170 cm is approximately 5 feet 6.9 inches, or about 5'7" rounded.
How many km is a marathon?
A full marathon is 42.195 kilometers (26.2 miles). A half marathon is 21.0975 km (13.1 miles).
What is 10 mm in inches?
10 mm equals 0.3937 inches, which is roughly 25/64 inch — slightly less than 3/8 inch.
Is 1 meter exactly 3 feet?
No. One meter is 3.2808 feet, which is 3 feet 3.37 inches. The metric-imperial relationship doesn't produce round numbers in either direction.
Does the length converter store my data?
No. All conversions run in your browser. No measurements are sent to a server or stored after you close the page.
How accurate are the conversions?
Conversions use exact international standard ratios (e.g. 1 inch = 25.4 mm exactly). Results are displayed to several decimal places with rounding only for display — suitable for most practical and scientific purposes.
By the Numbers
- The metre is defined as the distance light travels in vacuum in exactly 1/299,792,458 of a second (BIPM, 1983)
- The United States is one of only 3 countries that have not officially adopted the metric system (alongside Myanmar and Liberia)
- The agreement fixing 1 inch = exactly 25.4 mm was signed in 1959 by the U.S., U.K., Canada, Australia, New Zealand, and South Africa
- The metric system was first formally proposed in 1670 and adopted internationally via the Metre Convention in 1875