E. Spatial Sense · Angles, Rectangles, Grids and Measurement

Capacity: Millilitres and Litres

E2.1About 35 minutes

Learning goals

I can explain that 1 litre is the same as 1000 millilitres.
I can use benchmarks to estimate capacity in millilitres and litres.
I can read the scale on a measuring cup.
I can choose millilitres or litres for a container.

Words to know

capacity
How much a container can hold.

litre (L)
A metric unit of capacity. A carton of milk often holds 1 L.

millilitre (mL)
A very small metric unit of capacity. 1000 mL = 1 L.

scale
The marks and numbers on a measuring tool, like the lines on a measuring cup.

Remember from Grade 3

In Grade 3 you measured capacity with cups and scoops. You learned to fill each scoop level and fill the container to the top. Now you will use standard units: litres and millilitres.

Let's start with a pitcher of juice

You are making juice for a party. The recipe says to add 1 L of water. Your measuring cup only goes up to 500 mL. What do you do?

To answer, you need to know how litres and millilitres are related.

A large glass pitcher of orange juice beside a small empty pitcher and two empty glasses on a counter. — The big pitcher holds about a litre or more of juice. Each glass holds only a few hundred millilitres, so it takes several glasses to empty the pitcher. AI-generated image

Litres and millilitres

A litre (L) is a medium amount. Many cartons of milk or juice hold 1 L. We use litres for bigger containers: a pot, a bucket, a bathtub, a fish tank.
A millilitre (mL) is a tiny amount, only about 20 drops of water. A measuring teaspoon holds 5 mL. We use millilitres for smaller amounts: medicine, a juice box, a glass of water, a can of soup.

1 litre = 1000 millilitres

The word milli means one thousandth. It takes 1000 millilitres to make one litre.

Benchmark	About how much?
A measuring teaspoon	5 mL
A small juice box	often 200 mL (check the label)
A Canadian metric measuring cup	250 mL
A carton of milk	often 1 L
An Ontario bag of milk (holds 3 smaller bags)	4 L

Benchmarks for capacity. Labels give the exact amount.

Four 250 mL glasses of water fill a 1 L container, because 250 + 250 + 250 + 250 = 1000 mL.

Reading a measuring cup

A measuring cup has a scale of marks up the side. Look at the numbers to see how much each small mark is worth. On the cup below, the long marks are labelled every 100 mL, and there is a short mark halfway between each pair, so each short mark is 50 mL.

Put the cup on a flat table and look at the water from the side, at eye level.

A measuring cup with marks every 50 mL. The water is at 350 mL.

Worked example

Example 1: The juice problem

Your measuring cup holds 500 mL. How many full cups make 1 L?

1 L = 1000 mL.
500 mL + 500 mL = 1000 mL.
So 2 full cups make 1 L.

2 cups of 500 mL make 1 L.

Worked example

Example 2: Litres to millilitres

A pot of soup holds 3 L. How many millilitres is that?

Each litre is 1000 mL.
3 × 1000 = 3000.

3 L = 3000 mL

Worked example

Example 3: Mixed units

A jug has 1750 mL of water. Write it in litres and millilitres. Is it more or less than 2 L?

1750 = 1000 + 750.
1000 mL = 1 L, with 750 mL left over.
2 L = 2000 mL. 1750 is less than 2000.

1750 mL = 1 L 750 mL, which is less than 2 L (250 mL less).

A neat connection

1 mL of water has a mass of about 1 g, and 1 L of water has a mass of about 1 kg. That's why a 1 L carton was our benchmark for 1 kg in the last lesson! (This works for water. Other things, like oil or honey, have different masses.)

Math talk: estimate first

Before you measure, estimate: "I think this mug holds about 300 mL, because it holds a little more than a measuring cup." Then measure and compare. Your estimates will get better with practice.

Just for fun

A teaspoon holds about 5 mL. To fill a 1 L carton one teaspoon at a time, you'd need about 200 trips. Better pack a snack!

Hands-on activity

Water lab

You need: a measuring cup with mL marks, a measuring teaspoon, an empty 1 L carton or bottle, and 4 containers from the kitchen (a mug, a glass, a bowl, a small pot).

Grown-up note: do this at the sink or outside, and wipe spills right away so nobody slips.

Fill the teaspoon with water and pour it into the measuring cup. Can you even see 5 mL on the scale? That's how small a millilitre is!
Estimate how much each kitchen container holds. Write your estimates.
Fill each container to the top with water, then pour it into the measuring cup to measure. Write the real amounts.
Use the measuring cup to pour exactly 1000 mL into the empty 1 L carton. Did it fill to the top (or close)?
Order the containers from least to greatest capacity.

Math talk: "Which container surprised you? Was its capacity more or less than you estimated?"

Your turn

How many millilitres are in 1 L?

Change 4 L to millilitres.

Change 2000 mL to litres.

Would you measure the capacity of a bathtub in mL or L?

Would you measure a dose of medicine in mL or L?

How many 250 mL glasses can you fill from a 1 L carton?

Half a litre is how many millilitres?

More practice: warm-up

What does mL stand for?

Which is bigger: 1 L or 1 mL?

About how much does a measuring teaspoon hold?

Change 6 L to millilitres.

Which unit would you use for a swimming pool: mL or L?

More practice: on your own

Order from least to greatest: 1 L 200 mL, 900 mL, 2 L.

A juice box holds 200 mL. How many juice boxes would fill a 1 L jug?

Sara drank 350 mL of water in the morning and 400 mL in the afternoon. How much did she drink in all? Is it more or less than 1 L?

A measuring cup has a long mark every 100 mL and one short mark between each pair of long marks. What is each short mark worth? The water is at the short mark between 200 and 300. How much water is there?

Ben says a mug holds about 3 L. Is that a reasonable estimate? Explain.

Challenge

A recipe needs 1 L 500 mL of water. You only have a 250 mL measuring cup. How many full cups do you need?

A 2 L bottle of water is full. You pour out three glasses of 300 mL each. How much water is left?

About what mass of water is in a full 2 L bottle? Use what you know about mL and grams.

Check your understanding

Quiz

How many millilitres are in 1 litre?

Which holds about 5 mL?

Which unit is best for the capacity of a fish tank?

3000 mL is the same as...

How many 500 mL bottles fill a 2 L jug?

Which amount is the greatest?

For parents and teachers

Big idea: The Ontario curriculum (E2.1) asks Grade 4 students to explain the relationship between litres and millilitres (1 L = 1000 mL) and to use benchmarks to estimate capacity. Good benchmarks: a measuring teaspoon is 5 mL, a Canadian metric measuring cup is 250 mL, and a milk carton is often 1 L.

Common difficulties:

Comparing numbers without converting. 900 mL is not more than 2 L. Change to the same unit first.
Reading scales. Children often assume each mark is 1. Help them figure out what each mark is worth by looking at the labelled numbers.
Reading from above. Water levels should be read at eye level on a flat surface.

How to help: Cooking and baking are perfect practice. Let your child measure liquids for a recipe, read labels on bottles and cartons, and estimate how many glasses a jug will fill.