The Metric System - Measurement Built on Tens
The metric system is the world's most widely used system of measurement. Built on a foundation of ten, it makes converting between units simple and logical. Scientists, engineers, and most countries worldwide use it as the standard.
What Is the Metric System?
The metric system (formally the International System of Units, SI) uses seven base units. All other units are derived from these. The power of the metric system lies in its prefixes – each one represents a power of ten.
The Seven SI Base Units
| Quantity | Unit | Symbol |
|---|---|---|
| Length | Metre | m |
| Mass | Kilogram | kg |
| Time | Second | s |
| Temperature | Kelvin | K |
| Electric current | Ampere | A |
| Amount of substance | Mole | mol |
| Luminous intensity | Candela | cd |
Metric Prefixes
| Prefix | Symbol | Meaning | Example |
|---|---|---|---|
| Tera | T | 10¹² | 1 TB = 10¹² bytes |
| Giga | G | 10&sup9; | 1 GHz = 10&sup9; Hz |
| Mega | M | 10&sup6; | 1 MW = 10&sup6; W |
| Kilo | k | 10³ | 1 km = 1,000 m |
| Hecto | h | 10² | 1 hm = 100 m |
| Deca | da | 10¹ | 1 dam = 10 m |
| (Base unit) | — | 10&sup0; = 1 | metre, gram, litre |
| Deci | d | 10−¹ | 1 dm = 0.1 m |
| Centi | c | 10−² | 1 cm = 0.01 m |
| Milli | m | 10−³ | 1 mm = 0.001 m |
| Micro | µ | 10−&sup6; | 1 µm = 0.000001 m |
| Nano | n | 10−&sup9; | 1 nm = 10−&sup9; m |
Why the Metric System Is So Useful
- Every conversion is a multiple of 10 – just move the decimal point.
- The same prefixes apply to all quantities: kilogram, kilometre, kilolitre.
- It is consistent worldwide, reducing errors in science and trade.
Worked Examples
Convert 5.3 km to metres.
kilo = 10³, so × 1,000. 5.3 × 1,000 = 5,300 m.
Convert 4,200 ml to litres.
milli = 10−³, so ÷ 1,000. 4,200 ÷ 1,000 = 4.2 l.
Key Takeaways
- The SI system has 7 base units; all other units are derived from them.
- Prefixes (kilo, centi, milli, etc.) each represent a power of 10.
- Converting in the metric system always means multiplying or dividing by a power of 10.
Practice Questions
- Convert 2.8 kg to grams.
- Convert 3,500 mm to metres.
- How many centilitres are in 5 litres?
- A computer has 8 GB of RAM. How many megabytes is that?
- What does the prefix "mega" mean, and give a real-life example of its use?