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Year 3 Maths Volume & Capacity

Compare & order capacity

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Theory

Comparing and ordering capacity is a Year 3 measurement skill: deciding which container holds more or less, and lining capacities up from least to greatest. Capacity is measured in litres and millilitres, and the key fact is that 1 litre equals 1000 mL. This Year 3 maths page shows how to put capacities in the same unit, compare the numbers, and read measuring jugs. Curriculum: VC2M3M02 / AC9M3M02.

Capacity is how much a container can hold, usually a liquid. It is measured in litres (L) and millilitres (mL). A drink bottle might hold \(600\) mL, and a large milk carton holds \(2\) L.

The two units are joined by one fact: \(1\) litre \(= 1000\) millilitres. So a capacity written in litres can always be changed into millilitres, and back again.

To compare two capacities, first put them in the same unit, then compare the numbers. The bigger number holds more; the smaller number holds less. To order capacities, line them up from least to greatest, or from greatest to least.

Two measuring jugs filled to different levels Jug A is filled to 350 mL and Jug B is filled to 700 mL, so Jug B holds more water. 0 500 1000 mL Jug A 350 mL 0 500 1000 mL Jug B 700 mL
Both jugs use millilitres: \(700 > 350\), so Jug B holds more.
A measuring jug filled to the 1000 mL mark A measuring jug filled right to the 1000 mL line, showing that 1 litre is the same as 1000 millilitres. 0 500 1000 mL full to the top 1 L = 1000 mL
A jug filled to the top mark shows \(1\) L \(= 1000\) mL.

Comparing capacity does not need formulas, but these facts let you change every capacity into the same unit first.

\[ 1 \text{ L} = 1000 \text{ mL} \]
1 L =1000 mL
\[ 4 \text{ L} = 4000 \text{ mL} \]
4 L =4000 mL
\[ 1 \text{ L } 600 \text{ mL} = 1600 \text{ mL} \]
1 L 600 mL =1600 mL
Same unit first. To compare or order, change every capacity to millilitres, then compare the numbers. The bigger number holds more, so \(1\) L \(= 1000\) mL is more than \(980\) mL.
Same amount, different names. \(2\) L \(50\) mL and \(2050\) mL hold the same amount. Watch the zero: \(2\) L \(50\) mL is not \(2500\) mL.

How to compare and order capacities

  1. Same unit. Change every capacity to millilitres, using \(1\) L \(= 1000\) mL.
  2. Compare the numbers. The bigger number holds more; the smaller number holds less.
  3. Order or answer. Line the numbers up from least to greatest (or greatest to least), or subtract to find how much more one holds.
Example 1 — Which holds the most
Three cups hold \(320\) mL, \(275\) mL and \(410\) mL. Which cup holds the most?
Solution
\(\text{same unit}\)\(:\)\(320,\ 275,\ 410 \text{ mL}\)
\(\text{compare}\)\(:\)\(410 > 320 > 275\)
410>320>275

The \(410\) mL cup holds the most.

Example 2 — Compare across units
Which is larger: \(1\) L \(400\) mL or \(1350\) mL?
Solution
\(1 \text{ L } 400 \text{ mL}\)\(=\)\(1400 \text{ mL}\)
\(1400\)\(>\)\(1350\)
1400>1350

So \(1\) L \(400\) mL is larger.

Example 3 — Order least to greatest
Put \(950\) mL, \(1\) L and \(1\) L \(250\) mL in order from least to greatest.
Solution
\(1 \text{ L}\)\(=\)\(1000 \text{ mL}\)
\(1 \text{ L } 250 \text{ mL}\)\(=\)\(1250 \text{ mL}\)
\(\text{order}\)\(:\)\(950 < 1000 < 1250\)
950<1000<1250

In order: \(950\) mL, \(1\) L, \(1\) L \(250\) mL.

Example 4 — How much more
Read the two jugs. How much more water is in Jug P than in Jug Q?
Two measuring jugs, Jug P and Jug Q Jug P is filled to 800 mL and Jug Q is filled to 450 mL. 0 500 1000 mL Jug P 0 500 1000 mL Jug Q
Solution
\(\text{Jug P}\)\(=\)\(800 \text{ mL}\)
\(\text{Jug Q}\)\(=\)\(450 \text{ mL}\)
\(800 - 450\)\(=\)\(350 \text{ mL}\)
800-450=350

Jug P holds \(350\) mL more.

Example 5 — Difference in L and mL
A bucket holds \(4\) L. A watering can holds \(2\) L \(300\) mL. How much more does the bucket hold? Give the answer in litres and millilitres.
Solution
\(4 \text{ L}\)\(=\)\(4000 \text{ mL}\)
\(2 \text{ L } 300 \text{ mL}\)\(=\)\(2300 \text{ mL}\)
\(4000 - 2300\)\(=\)\(1700 \text{ mL}\)
\(1700 \text{ mL}\)\(=\)\(1 \text{ L } 700 \text{ mL}\)

The bucket holds \(1\) L \(700\) mL more.

Example 6 — Equal capacities
Bottle P holds \(2\) L \(50\) mL, bottle Q holds \(2050\) mL and bottle R holds \(2\) L \(500\) mL. Which two hold the same amount? Order them from greatest to least.
Solution
\(\text{P}\)\(=\)\(2000 + 50 = 2050 \text{ mL}\)
\(\text{Q}\)\(=\)\(2050 \text{ mL}\)
\(\text{R}\)\(=\)\(2000 + 500 = 2500 \text{ mL}\)

P and Q hold the same amount. From greatest to least: R, then P and Q (equal).

Common pitfalls

Same unit first. Watch out for comparing litres with millilitres straight away. Change \(1\) L to \(1000\) mL, then compare the numbers.
The bigger number is not always more. \(980\) mL looks bigger than \(1\) L, but \(1\) L \(= 1000\) mL, so \(1\) L holds more. Always check the units.
Rename carefully. \(1\) L \(80\) mL is \(1080\) mL, not \(180\) mL, because one litre is \(1000\) mL.

Frequently asked questions

How do you compare two capacities?

Change both capacities to the same unit, usually millilitres, then compare the numbers. The bigger number holds more. For example, \(1\) L \(= 1000\) mL, which is more than \(980\) mL.

How many millilitres are in a litre?

There are \(1000\) millilitres in \(1\) litre. So \(1\) L \(= 1000\) mL, and \(4\) L \(= 4000\) mL.

Which is bigger, 1 litre or 980 mL?

One litre is bigger. Change \(1\) L to \(1000\) mL, then compare. \(1000\) mL is more than \(980\) mL, so \(1\) litre holds more.

How do you put capacities in order from least to greatest?

Change every capacity to millilitres, then line the numbers up from smallest to largest. For \(950\) mL, \(1\) L and \(1\) L \(250\) mL you get \(950 < 1000 < 1250\), so the order is \(950\) mL, \(1\) L, \(1\) L \(250\) mL.

What is capacity in maths?

Capacity is how much a container can hold, usually a liquid. It is measured in litres and millilitres.

How do you change litres to millilitres?

Multiply the number of litres by \(1000\), then add any extra millilitres. So \(1\) L \(600\) mL is \(1000 + 600 = 1600\) mL.

How much more is needed to make 1 litre?

Change \(1\) L to \(1000\) mL and subtract what is already there. A jug with \(350\) mL needs \(1000 - 350 = 650\) mL more.

How do you order capacities from greatest to least?

Change every capacity to millilitres, then write the numbers from largest to smallest. Equal numbers hold the same amount, so they sit side by side.

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