What is the metric system?
The metric system is a decimal measurement system based on units such as metres, grams, litres and Celsius. It makes conversions easier because most metric units move in tens, hundreds and thousands.
The metric system is a measurement system that uses decimal-based units such as metres for length, kilograms and grams for weight or mass, litres for volume and Celsius for temperature.
Because metric units are based around powers of 10, many conversions are simpler than imperial conversions. For example, 1 metre is 100 centimetres and 1 kilogram is 1,000 grams.
Why the metric system matters
The metric system is used widely in science, education, trade, packaging and everyday measurement. In the UK, many official and retail measurements use metric units, even though imperial units are still common in everyday speech.
That is why UK users often need to convert between systems, such as centimetres to inches, kilograms to pounds, litres to pints and kilometres to miles.
Common metric units
The most common everyday metric units are used for length, weight, volume and temperature.
| Measurement type | Common metric units | Everyday example |
|---|---|---|
| Length | millimetres, centimetres, metres, kilometres | Height, room sizes, road distances |
| Weight or mass | grams, kilograms | Food packets, body weight, parcels |
| Volume | millilitres, litres | Drinks, fuel, cooking liquids |
| Temperature | Celsius | Weather, heating, cooking temperatures |
Why metric conversions are often easier
The metric system is decimal, so many conversions involve multiplying or dividing by 10, 100 or 1,000.
1 kilometre = 1,000 metres
1 kilogram = 1,000 grams
1 litre = 1,000 millilitres
This is different from many imperial units, where conversions may use factors such as 12 inches in a foot, 3 feet in a yard or 14 pounds in a stone.
Metric vs imperial units
Metric and imperial units measure similar things, but they use different unit sizes and conversion rules. Metric units are based on decimal steps, while imperial units use older measurement relationships.
| Metric unit | Common imperial comparison | Used for |
|---|---|---|
| centimetre | inch | Small lengths and height |
| metre | foot or yard | Room sizes and distances |
| kilometre | mile | Long distances |
| kilogram | pound or stone | Weight and mass |
| litre | pint or gallon | Liquids and volume |
For a fuller comparison, see the metric vs imperial units guide.
Metric conversion examples
Here are simple examples of metric conversions:
| Conversion | Calculation | Result |
|---|---|---|
| 250 centimetres to metres | 250 ÷ 100 | 2.5 metres |
| 3.2 kilograms to grams | 3.2 × 1,000 | 3,200 grams |
| 750 millilitres to litres | 750 ÷ 1,000 | 0.75 litres |
| 5 kilometres to metres | 5 × 1,000 | 5,000 metres |
The metric system in the UK
The UK uses a mix of metric and imperial in everyday life. Food packaging, medicine, many product sizes and official measurements commonly use metric units. Road distances and speed limits still use miles and miles per hour.
People may also describe height in feet and inches, body weight in stone and pounds, drinks in pints and property space in square feet. That is why a UK-friendly converter should handle both systems clearly.
Quick answers
| Question | Answer |
|---|---|
| What is the metric system? | A decimal measurement system using units such as metres, grams, litres and Celsius. |
| Why is it easier to convert metric units? | Many metric conversions use powers of 10, such as 100 centimetres in a metre. |
| Is the UK metric or imperial? | The UK uses both. Metric is common in official and retail settings, while imperial is still used in roads, height, body weight and pints. |
| What is the opposite of metric? | The usual comparison is imperial units, such as inches, feet, miles, pounds and pints. |
FAQs
What does metric system mean?
The metric system is a decimal-based way of measuring length, weight, volume, temperature and other quantities. Everyday metric units include metres, kilograms, litres and Celsius.
Is a centimetre part of the metric system?
Yes. A centimetre is a metric length unit. There are 100 centimetres in 1 metre.
Is a kilogram metric?
Yes. A kilogram is a metric unit used for weight or mass in everyday contexts. There are 1,000 grams in 1 kilogram.
Why do UK people still use imperial units?
Some imperial units remain common in everyday UK life, especially miles, miles per hour, feet and inches, stone and pounds, and pints.