What is micrometre?
A micrometre, also called a micron, is a unit of length equal to one millionth of a metre. It is used in microscopy, semiconductor fabrication, and the measurement of fine particles and biological cells.
Real-world uses
Micrometres (microns) are used to measure biological cells, bacteria, semiconductor chip features, and fine particle sizes in air quality monitoring. Paint film thickness, fibre diameters, and precision machining tolerances are also specified in µm.
History
The micrometre was formalized with SI prefix standardization in the 20th century. The term "micron" was officially revoked by the SI in 1967 in favour of "micrometre," though "micron" persists informally in many industries.
Common mistakes
Using the symbol "u" instead of the correct "µ" (Greek mu). Also, confusing micrometres with nanometres—a human hair is about 70 µm wide, not 70 nm.
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.
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 micrometre = 1.000000e-09 kilometre
1 kilometre = 1,000 metre
How to convert micrometre to kilometre
To convert micrometre to kilometre, multiply the value by 1.000000e-09.
To convert kilometre back to micrometre, multiply by 1.000000e+09.
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: micrometre to kilometre
| micrometre | kilometre |
|---|---|
| 0.1 | 1.000000e-10 |
| 0.5 | 5.000000e-10 |
| 1 | 1.000000e-09 |
| 2 | 2.000000e-09 |
| 5 | 5.000000e-09 |
| 10 | 1.000000e-08 |
| 25 | 2.500000e-08 |
| 50 | 5.000000e-08 |
| 100 | 1.000000e-07 |
| 250 | 2.500000e-07 |
| 500 | 5.000000e-07 |
| 1,000 | 0.000001 |
Common values
| micrometre | kilometre | |
|---|---|---|
| Height of a door | 2,100,000 micrometre | 0.0021 kilometre |
| Basketball court length | 28,000,000 micrometre | 0.028 kilometre |
| Football field (soccer) | 105,000,000 micrometre | 0.105 kilometre |
| Marathon distance | 4.219500e+10 micrometre | 42.195 kilometre |
| Altitude of a cruising airplane | 1.066800e+10 micrometre | 10.668 kilometre |