What is kilometre?
A kilometre is a metric unit of length equal to 1,000 metres. It is the standard unit for road distances, route planning, and geographic measurements in most countries.
Real-world uses
Kilometres are the standard unit for road distances, city-to-city navigation, and speed limits in most countries outside the United States. Marathon runners track their pace in minutes per kilometre, and GPS devices report distances in km.
History
Introduced as part of the metric system in France in 1795. The prefix "kilo-" comes from the Greek word "chilioi" meaning thousand. It became the global standard for road distances as the metric system spread in the 19th and 20th centuries.
Common mistakes
Assuming 1 mile equals 1 kilometre—a mile is actually about 1.609 km. Another error is mispronouncing it as "kil-AH-meter" instead of "KIL-o-metre," which changes the implied meaning.
What is centimetre?
A centimetre is a metric unit of length equal to one hundredth of a metre. It is commonly used for everyday measurements such as clothing sizes, body height, and small object dimensions.
Real-world uses
Centimetres are widely used in clothing measurements, body height in medical records (outside the US), screen sizes in some markets, and school rulers. Tailors and dressmakers rely on centimetre tape measures for precise garment fitting.
History
The centimetre was established as part of the original metric system in the 1790s. It served as the base length unit in the now-superseded CGS (centimetre-gram-second) system used extensively in physics until the mid-20th century.
Common mistakes
Forgetting that there are 2.54 cm in one inch, not 2.5. Also, confusing cm² (area) with cm (length) when specifying material dimensions.
When is this conversion used?
Road distances and speed limits are posted in kilometres in most countries and miles in the US and UK, making this conversion essential for international drivers and route planning. Screen sizes, paper dimensions, and clothing measurements often require converting between centimetres and inches, especially when shopping internationally.
Worked examples
1 kilometre = 100,000 centimetre
1 centimetre = 0.01 metre
How to convert kilometre to centimetre
To convert kilometre to centimetre, multiply the value by 100,000.
To convert centimetre back to kilometre, multiply by 0.00001.
Measurement standards
The metre is one of seven SI base units, maintained by the International Bureau of Weights and Measures (BIPM). Since 2019, it is defined by fixing the numerical value of the speed of light in vacuum to exactly 299,792,458 metres per second.
Did you know?
A human hair is roughly 70 micrometres wide, while a single gold atom measures about 0.144 nanometres in diameter — meaning you could line up nearly half a million atoms across the width of one hair.
Quick reference: kilometre to centimetre
| kilometre | centimetre |
|---|---|
| 0.1 | 10,000 |
| 0.5 | 50,000 |
| 1 | 100,000 |
| 2 | 200,000 |
| 5 | 500,000 |
| 10 | 1,000,000 |
| 25 | 2,500,000 |
| 50 | 5,000,000 |
| 100 | 10,000,000 |
| 250 | 25,000,000 |
| 500 | 50,000,000 |
| 1,000 | 100,000,000 |
Common values
| kilometre | centimetre | |
|---|---|---|
| Height of a door | 0.0021 kilometre | 210 centimetre |
| Basketball court length | 0.028 kilometre | 2,800 centimetre |
| Football field (soccer) | 0.105 kilometre | 10,500 centimetre |
| Marathon distance | 42.195 kilometre | 4,219,500 centimetre |
| Altitude of a cruising airplane | 10.668 kilometre | 1,066,800 centimetre |