Metre facts for kids
Quick facts for kids metre |
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Replicas of historical metric standards, including a copy of the Mètre des Archives
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| General information | |
| Unit system | SI |
| Unit of | length |
| Symbol | m |
| Conversions | |
| 1 m in ... | ... is equal to ... |
| Imperial/US units | |
| Nautical units | ≈ 0.00053996 nmi |
The metre (pronounced MEE-ter, symbol: m) is the basic unit for measuring length in the International System of Units (SI). Think of the SI as the world's standard way to measure things, like a common language for scientists and engineers everywhere.
Since 2019, the metre has been defined using the speed of light. It's the distance light travels in a tiny fraction of a second in empty space. This makes the metre a very precise and unchanging measurement.
The idea of the metre started in France in 1791. It was first imagined as one ten-millionth of the distance from the equator to the North Pole, passing through Paris. This was a huge project to measure a part of the Earth's circumference.
Over time, the definition of the metre became more exact. In 1799, it was based on a special metal bar. Later, in 1960, scientists used the light from a special gas called krypton-86 to define it. The current definition, using the speed of light, was adopted in 1983 and refined in 2019. This ensures that the metre is always the same, no matter where you are.
Contents
Where Did the Word "Metre" Come From?
The word "metre" comes from ancient Greek words like metreo (meaning "I measure") and metron (meaning "a measure"). These words were used for measuring things in the physical world. They also meant things like rhythm in poetry or being balanced in your actions.
In most English-speaking countries, like the UK, Canada, and Australia, we spell it metre. However, in the United States and the Philippines, it's spelled meter. Both words refer to the same unit of length.
How We Use Metres for Different Sizes
The metre is a great unit, but sometimes we need to measure things much smaller or much larger. That's where SI prefixes come in handy! These prefixes are added to "metre" to show multiples (bigger amounts) or submultiples (smaller amounts) of a metre.
For example:
- A kilometre (km) is 1,000 metres. We use kilometres to measure long distances, like the length of a road.
- A centimetre (cm) is one-hundredth of a metre. It's useful for measuring smaller things, like the length of a pencil.
- A millimetre (mm) is one-thousandth of a metre. We use millimetres for very small measurements, like the thickness of a coin.
Here's a table showing some common prefixes:
| Submultiples | Multiples | ||||
|---|---|---|---|---|---|
| Value | SI symbol | Name | Value | SI symbol | Name |
| 10−1 m | dm | decimetre | 101 m | dam | decametre |
| 10−2 m | cm | centimetre | 102 m | hm | hectometre |
| 10−3 m | mm | millimetre | 103 m | km | kilometre |
| 10−6 m | μm | micrometre | 106 m | Mm | megametre |
| 10−9 m | nm | nanometre | 109 m | Gm | gigametre |
| 10−12 m | pm | picometre | 1012 m | Tm | terametre |
| 10−15 m | fm | femtometre | 1015 m | Pm | petametre |
| 10−18 m | am | attometre | 1018 m | Em | exametre |
| 10−21 m | zm | zeptometre | 1021 m | Zm | zettametre |
| 10−24 m | ym | yoctometre | 1024 m | Ym | yottametre |
| 10−27 m | rm | rontometre | 1027 m | Rm | ronnametre |
| 10−30 m | qm | quectometre | 1030 m | Qm | quettametre |
You might hear older terms like "micron" instead of "micrometre" or "millimicron" instead of "nanometre." However, it's better to use the standard names like micrometre and nanometre.
Comparing the Metre to Other Units
Even though the metre is part of the worldwide SI system, some countries, like the United States, still use older units of length. It's helpful to know how the metre compares to these.
- One metre is a little longer than a yard. Imagine a football field; a metre is about the same length as one yard plus a few inches.
- One metre is about 3.28 feet. That's roughly three feet and three inches.
- One metre is about 39.37 inches. This means it's a bit longer than a standard yardstick (which is 36 inches).
Here's a simple trick to remember: one metre is almost exactly 3 feet and 3 and 3/8 inches. This is often called the "three 3s" rule!
Long ago, people used many different ways to measure length. For example, the ancient Egyptian cubit was about half a metre. The old Parisian toise (like a fathom) was a bit less than 2 metres. These old units show how important it was to create a standard, worldwide system like the metre.
See also
In Spanish: Metro para niños
- ISO 1 – A standard for temperature when measuring length
- Metric prefix – Learn more about prefixes like kilo, centi, and milli
- Metrication – How countries switch to using the metric system
