UK Primary (3-6) Units of capacity (and conversions)
Lesson Capacity is the maximum amount something can hold. For example, the carton below has a capacity of $1$1 L because it can hold one litre of juice. ## Common Units of Measurement for Capacity

How you measure capacity depends on where you live. Most of the world follows the metric system. However, the imperial system is still used in countries such as the United Kingdom and the USA.

In the metric system, millilitres (mL), litres (L), kilolitres (kL) and megalitres (ML) are common units of capacity.

## Which Unit Should You Choose?

As a general rule, we try to pick a unit that is appropriate for the size of the container you are measuring. For example, a bottle of juice is much smaller than a dam that supplies a town with water. So we'd use a smaller unit of measurement to measure a bottle of juice and a larger unit of measurement to measure a dam.

This helps people understand the size of the object being measured. For example, I could say an olympic size swimming pool holds $2500000000$2500000000 mL. However, that number is really big! It would be more clear to say that it holds $2500000$2500000 L or even $2500$2500 KL.

## Converting between Units of Capacity

Converting means changing. For example, I converted the size of the swimming pool from millilitres into litres. You may also have already looked at how to convert grams into kilograms or metres into centimetres

To convert units of capacity, we just need to know you many of one thing makes up another.

Here is a conversion chart:

Unit Equal to
Millilitre (mL) $1$1 $cm^3$cm3
Litre (L) $1000$1000 mL
Kilolitre (kL) $1000$1000 L
Megalitre (ML) $1000$1000 kL or $1000000$1000000 L
Remember!
• When you convert from a larger unit to a smaller unit (e.g. L to mL), you multiply.
• When you convert from a smaller unit to a larger unit (e.g. mL to L), you divide.

#### Worked Examples ##### Question 1

How much water is in the jug? Give your answer in litres.

Think: This jug is showing an amount halfway between $400$400 and $600$600 mL? How would we convert this to L?

Do: This jug has $500$500 mL of water in it. There are $1000$1000 mL in $1$1 L. So this jug has $0.5$0.5 L of water in it.

##### Question 2

Convert $1.54$1.54 litres to millilitres.

1. $1.54$1.54 litres = $\editable{}$ millilitres