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GRADE 6 · MATHEMATICS

Metric Units and Conversions

Learn how to measure and convert length, mass and capacity using the metric system. Understand the relationships between millimetres, centimetres, metres, kilometres, grams, kilograms, millilitres and litres.

Learning time: approximately 25–30 minutes · Beginner level

What You Will Learn

Recognise common metric units for length, mass and capacity.
Convert between related metric units.
Choose a sensible unit for a measurement.
Solve everyday measurement problems.
Check whether a conversion makes a quantity larger or smaller.

1. The Metric System

The metric system is a measurement system used in many countries. It is based on groups of ten, so converting between common units often involves multiplying or dividing by 10, 100 or 1,000.

The prefixes help you remember the size of a unit:

kilo- means 1,000 times the base unit.
centi- means one hundredth of the base unit.
milli- means one thousandth of the base unit.

Important: Convert measurements within the same type. Length converts to length, mass to mass, and capacity to capacity. You cannot convert metres directly into kilograms.

2. Units of Length

Length tells us how long, tall or far something is.

Unit	Relationship	Example
1 kilometre (km)	1,000 metres	Distance between towns
1 metre (m)	100 centimetres	Height of a door
1 centimetre (cm)	10 millimetres	Width of a fingernail
1 metre (m)	1,000 millimetres	Small object measurements

Example A: Convert 3.5 metres to centimetres.

1 m = 100 cm, so multiply by 100.

3.5 × 100 = 350 cm.

Example B: Convert 4,200 metres to kilometres.

1 km = 1,000 m, so divide by 1,000.

4,200 ÷ 1,000 = 4.2 km.

Example C: Convert 86 millimetres to centimetres.

10 mm = 1 cm, so divide by 10.

86 ÷ 10 = 8.6 cm.

3. Units of Mass

Mass tells us how much matter an object contains. In everyday conversation, people sometimes say weight when they mean mass.

Unit	Relationship	Example
1 kilogram (kg)	1,000 grams	A bag of rice
1 gram (g)	1,000 milligrams	A small amount of medicine

Example: Convert 2.75 kg to grams.

1 kg = 1,000 g, so 2.75 × 1,000 = 2,750 g.

Another example: Convert 640 g to kilograms.

640 ÷ 1,000 = 0.64 kg.

4. Units of Capacity

Capacity tells us how much liquid a container can hold.

Unit	Relationship	Example
1 litre (L)	1,000 millilitres	A large drink bottle
1 millilitre (mL)	One thousandth of a litre	A spoonful of liquid

Example: Convert 1.8 L to millilitres.

1.8 × 1,000 = 1,800 mL.

Example: Convert 350 mL to litres.

350 ÷ 1,000 = 0.35 L.

5. A Reliable Conversion Method

Identify the quantity: Is it length, mass or capacity?
Write the relationship: For example, 1 km = 1,000 m.
Choose the operation: Convert to a smaller unit by multiplying; convert to a larger unit by dividing.
Calculate: Move the decimal point the correct number of places or use multiplication/division.
Check the result: A measurement in smaller units should usually have a larger number.

Larger unit → smaller unit: multiply

Smaller unit → larger unit: divide

Use the exact conversion factor: 10, 100 or 1,000 as appropriate.

6. Everyday Word Problems

Distance walked

A student walks 1.25 km to a park. How many metres is this?

1.25 × 1,000 = 1,250 m.

Fruit purchased

A shopper buys 1.4 kg of apples. How many grams is that?

1.4 × 1,000 = 1,400 g.

Water in a jug

A jug contains 750 mL of water. How many litres is this?

750 ÷ 1,000 = 0.75 L.

7. Common Mistakes

Multiplying when you should divide: When converting 500 cm to metres, divide by 100. The answer is 5 m, not 50,000 m.

Using the wrong conversion factor: 1 m = 100 cm, while 1 km = 1,000 m. Learn the relationship for each pair.

Forgetting the unit: Write cm, m, kg or L after the number.

Mixing measurement types: Length, mass and capacity are different quantities.

Not checking the size: 2,000 g is 2 kg. The number becomes smaller when grams are converted to kilograms.

8. Practice Exercises

Convert 6 m to centimetres.
Convert 3.2 km to metres.
Convert 450 cm to metres.
Convert 2.6 kg to grams.
Convert 1,250 mL to litres.
A ribbon is 275 cm long. How many metres is it?

Show practice answers

600 cm.
3,200 m.
4.5 m.
2,600 g.
1.25 L.
275 ÷ 100 = 2.75 m.

10. Free Printable Worksheet

Print this worksheet or save it as a PDF.

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