What is metre?
The metre is the SI base unit of length. It is used globally in science, engineering, geography, and everyday measurement as the standard reference for distance.
Real-world uses
The metre is the standard unit for everyday measurements worldwide, from room dimensions and furniture sizes to athletic track events like the 100 m sprint. Engineers, architects, and scientists use it as the fundamental length reference in the SI system.
History
Originally defined in 1793 during the French Revolution as one ten-millionth of the distance from the North Pole to the equator along a meridian through Paris. Since 1983, it is defined by the speed of light in vacuum.
Common mistakes
Confusing "meter" (the measuring device) with "metre" (the unit of length) in British English. Also, people sometimes incorrectly assume 1 metre equals exactly 3 feet; it is actually about 3.281 feet.
What is millimetre?
A millimetre is a metric unit of length equal to one thousandth of a metre. It is used in precision manufacturing, medical imaging, engineering tolerances, and detailed technical specifications.
Real-world uses
Millimetres are essential in precision engineering, machining tolerances, and manufacturing specifications. Rainfall is reported in mm by meteorological services worldwide. Dentists measure cavity depths and orthodontic adjustments in millimetres.
History
Part of the original French metric system from the 1790s. The prefix "milli-" derives from the Latin "mille" meaning thousand, indicating one-thousandth of a metre. It became critical with the rise of precision manufacturing in the Industrial Revolution.
Common mistakes
Confusing millimetres with centimetres when reading rulers—each small division on a metric ruler is 1 mm, not 1 cm. Also, mixing up mm with mils (thousandths of an inch) in engineering contexts.
When is this conversion used?
This conversion is frequently needed in construction, architecture, and real estate where building codes may specify dimensions in one system while materials are sold in another.
Worked examples
1 metre = 1,000 millimetre
1 millimetre = 0.001 metre
How to convert metre to millimetre
To convert metre to millimetre, multiply the value by 1,000.
To convert millimetre back to metre, multiply by 0.001.
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: metre to millimetre
| metre | millimetre |
|---|---|
| 0.1 | 100 |
| 0.5 | 500 |
| 1 | 1,000 |
| 2 | 2,000 |
| 5 | 5,000 |
| 10 | 10,000 |
| 25 | 25,000 |
| 50 | 50,000 |
| 100 | 100,000 |
| 250 | 250,000 |
| 500 | 500,000 |
| 1,000 | 1,000,000 |
Common values
| metre | millimetre | |
|---|---|---|
| Height of a door | 2.1 metre | 2,100 millimetre |
| Basketball court length | 28 metre | 28,000 millimetre |
| Football field (soccer) | 105 metre | 105,000 millimetre |
| Marathon distance | 42,195 metre | 42,195,000 millimetre |
| Altitude of a cruising airplane | 10,668 metre | 10,668,000 millimetre |