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 nanometre?
A nanometre is a unit of length equal to one billionth of a metre. It is used to measure wavelengths of visible light, atomic radii, and dimensions of nanostructures in materials science.
Real-world uses
Nanometres are the standard unit in semiconductor fabrication (e.g., 5 nm chip processes), wavelength of visible light (380–700 nm), and molecular biology for measuring DNA strand widths and protein structures.
History
The nanometre gained prominence in the late 20th century with advances in electron microscopy and semiconductor technology. The prefix "nano-" comes from the Greek "nanos" meaning dwarf. It was officially adopted as an SI prefix in 1960.
Common mistakes
Confusing nanometres with angstroms—1 nm equals 10 angstroms. People also mistakenly equate "nano" products in marketing with actual nanometre-scale technology, which is not always the case.
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.
Worked examples
1 kilometre = 1.000000e+12 nanometre
1 nanometre = 1.000000e-09 metre
How to convert kilometre to nanometre
To convert kilometre to nanometre, multiply the value by 1.000000e+12.
To convert nanometre back to kilometre, multiply by 1.000000e-12.
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 nanometre
| kilometre | nanometre |
|---|---|
| 0.1 | 1.000000e+11 |
| 0.5 | 5.000000e+11 |
| 1 | 1.000000e+12 |
| 2 | 2.000000e+12 |
| 5 | 5.000000e+12 |
| 10 | 1.000000e+13 |
| 25 | 2.500000e+13 |
| 50 | 5.000000e+13 |
| 100 | 1.000000e+14 |
| 250 | 2.500000e+14 |
| 500 | 5.000000e+14 |
| 1,000 | 1.000000e+15 |
Common values
| kilometre | nanometre | |
|---|---|---|
| Height of a door | 0.0021 kilometre | 2.100000e+09 nanometre |
| Basketball court length | 0.028 kilometre | 2.800000e+10 nanometre |
| Football field (soccer) | 0.105 kilometre | 1.050000e+11 nanometre |
| Marathon distance | 42.195 kilometre | 4.219500e+13 nanometre |
| Altitude of a cruising airplane | 10.668 kilometre | 1.066800e+13 nanometre |