Dear Family, your Operation Maths guide to Capacity

Dear Family, your Operation Maths guide to Capacity

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Dear Family, below is a brief guide to understanding the topic of capacity, as well as some practical suggestions as to how you might support your children’s understanding at home. Also below, are a series of links to digital resources that will help both the children, and you, learn more about capacity. The digital resources are organised according to approximate class level:

Junior Infants to Second Class
You can also find class specific tips at the back of your child’s Operation Maths At Home book, for infants to second class, and in the Operation Maths Dear Family letters for third to sixth class.

Understanding Capacity

Capacity is the amount that a container, or something, can hold. Very closely related to this is volume, the amount of 3-D space that something takes up. And while both capacity and volume can be used to measure and describe the same objects/substances, there is a distinct difference. For example, the capacity of a empty plastic bottle may be 1 litre, but the volume of liquid it contains will be 0 cm3 (cubic centimetres). The same bottle, if full of water, will still have a capacity of 1 litre, but now, the volume of water contained within is 1 litre or 1,000 cm3.

Like length and weight, capacity has been traditionally measured using two separate systems: imperial units/US customary units (pints, gallons etc) and metric measures (millilitres, litres etc). In Ireland, the changeover to all metric measures began in the early 1970s and was completed in 2005 (although alcohol sold on draught is still sold by the pint ). Therefore, only metric measures are taught in Irish schools.

In school, the children are enabled to compare, estimate and measure capacity. In the infants classes, the children work with non-standard units (e.g. what is the capacity of the bottle in cups?) and then they are gradually introduced to the standard metric units of capacity i.e. litre (first class) and millilitre (third class). Children in the older classes will also be introduced to, and work with, more complex concepts related to capacity, such as calculating the volume of objects and converting from one unit of measurement to another (eg millilitres to litres).

Do you know how the metric system came into being? It has an interesting history! Watch this video and/or read this article. For more background info on capacity/volume you can read this post from Maths is Fun.

Practical Suggestions for all Children

  • Where possible allow your children to have opportunities for “water play”; this can be during bath time, playing in the sink when the washing up is done, having tea-time with a play tea-set, playing outside with a basin of water and containers, etc. Sand play, if available, should also be encouraged as children explore with “pouring” sand from one container to another. Read more about sand and water play here.
  • In school, the children are enabled to compare, estimate and measure capacity. You can reinforce this at home by asking the children to use their visual sense of capacity to compare and estimate which bottles, containers etc., hold more or hold less. Collect a selection of various types of bottles and containers and, if possible, remove any telling labels. Ask the children to line the containers up in order, starting with the one that they think holds the least. Fill this one with water, and then pour this water into the second container.
    • Does all the water fit? If no, then the first container holds more than the second container.
    • If yes, does the water from the first container fill the second container to the same level? Then they both hold the same amount.
    • Or is there space left at the top of the second container? Then it must hold more than the first container.
  • When estimating capacity, do the children realise that height and/or shape is not always indicative of capacity i.e. a taller but skinnier container may contain less than, or the same as, a shorter container.
  • When investigating capacity, try to conserve water; have a large basin handy, or do the water-pouring over a closed sink or bath so that the water can be reused. Why not even investigate the capacity of various containers as part of water play in the bath or sink?
  • Draw the children’s attention to capacity labels on bottles and containers, especially l for litres and ml for millilitres. Even children who may not yet know that there are 1,000ml in a litre, can examine labels and can use their number knowledge to identify the one which holds the most/least. If the item does not have a capacity label, does it have a label for a different unit of measurement and why is this? (e.g. perhaps g or kg for weight).
  • Is it good value? Keep a close eye on the capacity of various items when shopping (whether it be in the shops or online): while you’d expect that a 3l bottle of drink would be twice the price, or slightly less than twice the price, of a 1.5l bottle of the same drink, you would not expect it to be dearer – yet that can sometimes be the case! So involve the children in checking the capacity of items to make sure that you’re purchasing the item(s) that offers the best value for your money!
  • Find the items around your home that measure capacity (these are often called measuring instruments): kettles; liquid detergent caps and dispensers; medicine cups, spoons and syringes; buckets and basins; measuring jugs. Look carefully at the measuring scale, marked usually along the side, and get the children to try out these measuring instruments for themselves.
  • Involve your child in measuring capacity when cooking and baking. If using recipes, ask the children to calculate how much of each liquid ingredient would be required to make half, double, etc., of the amount/dish.
  • Enlist the help of older siblings if available. As they explain and support the younger members of the family, they will also be developing and consolidating their own knowledge and skills, especially communicating mathematically.
  • Draw the children’s attention to any other situation where capacity needs to be considered eg water conservation around the home, how much water we should drink daily, putting liquid detergent in the washing machine, the capacity of the household bins, the amount of rain forecast, recommended dosage for various medicines, buying enough paint for a particular room, purchasing fuel (eg petrol, diesel, home-heating oil), etc.

Digital Resources for Infants

NUMBERJACKS | The Container Drainer | S1E20 - YouTubeNumber Jacks: The Container Drainer



Watch Peep and the Big Wide World | Prime Video

Making lemonade: A video from Peep and the big Wide World, showing how some children used capacity as they made lemonade


Comparing Volume (Part 1) - YouTube

Full or Empty: A lesson from Matholia focusing on full and empty


Comparing Volume - YouTubeComparing volume: A lesson from Matholia which focuses on language such as greater than, less than, highest, lowest etc


Kidscreen » Archive » Big Bird goes to the big topFull and Empty with Grover: The Sesame Street favourites explore capacity. Other relevant clips include Elmo & Zoe Full and Empty, Kermit explains More and Less and The Two Headed Monster More and Less Milk

Happy Numbers Kindergarten: Work through the capacity activities in Module 3, Topic D. 



Splash Learn: Compare capacity



I Know It - Online Math PracticeI know it – Kindergarten: Scroll down to Measurement and select the holds more or less activities. 



IXL | Maths and English Practice

Holds more or less: a selection of games from You can do a number of free quizzes each day without having a subscription.


Math Games: Choose the Holds more or Less practice games from Junior and Senior Infants



Digital Resources for First and Second Classes

Describing Volume - YouTubeHalf full: video from Matholia showing how to describe capacity using “half full”.


Measuring Volume in Litres on VimeoMeasuring in litres: video from Matholia showing how to read the scale on a large container.


Mass: A series of video lessons from White Rose Maths, including, for Year 1,  Introduce capacity and volume and Measure capacity; for Year 2, Compare volume, Measure volume in millilitres, Measure volume in litres.


ictgames || html5 Home PageCapacity Countdown: Read the level of liquid on the scale and type in the capacity. Recommendation: Stick to litre and half litre option.


I Know It - Online Math PracticeI know it – First Grade: Scroll down to Measurement and select the holds more or less activities. There are similar activities in Second Grade 



IXL | Maths and English PracticeHolds more or less: a selection of games from You can do a number of free quizzes each day without having a subscription.



Math Games: Choose the Holds more or Less practice games from first and second class


Digital Resources for Third to Sixth Classes

Measurement IndexMetric Volume (capacity): Background information on volume (capacity) and litres and millilitres as the main metric units. At the end of the page there is a link to an activity, explaining how you could do some capacity activities at home.

Converting Millilitres to Litres and Millilitres - YouTubeMatholia – Volume: A number of video lessons on volume (capacity) that include Converting Litres and Millilitres to Millilitres, Converting Millilitres to Litres and Millilitres, Converting Litres to Millilitres, Addition, Subtraction, Multiplication and Division of Volume, Volume of a Liquid and Volume of Cubes and Cuboids

Capacity: A series of video lessons from White Rose Maths, including, for Year 3,  Measure capacity, Compare capacity, Add and subtract capacity; for Year 5, Metric units; for Year 6, Metric Measures, Convert metric measures, Calculate with metric measures, What is volume, Counting cubes, Volume of a cuboid

Khan Academy – Mass and Volume (Third Grade): Watch the videos and then answer the practice questions. Afterwards, for something more challenging,  look at the Fourth Grade activities on Estimating Volume and/or Converting Units of Volume. Or even the Fifth Grade activities on Metric Units of Volume. You can also register for a free Khan Academy account to record your progress and explore other topics/grades.  

Happy Numbers Third Grade: Pupils can do the weight and capacity activities in Module 2, Topic A.  



Mashup Math - YouTubeMashup Math – Volume: Video lessons that show how to Find the Volume of a Rectangular Prism and Finding the Volume of a Right Rectangular Prism Practice Problem


Measuring: Capacity - BBC TeachCapacity: Lots of useful information about capacity from BBC Skillswise, including a video highlighting capacity in the real world.

Beginner m Measuring capacity and reading scales converted - YouTubeUsing measuring instruments: a guide to understanding the scales on measuring jugs and using them correctly and accurately.

ictgames || html5 Home PageCapacity Countdown: Read the level of liquid on the scale and type in the capacity. Recommendation: work through the given options in order.


Topmarks on Twitter: "In our Coconut Ordering game you can compare ...

Coconut Ordering Game: Select Capacity to order amounts of l and ml


Splash Learn – Measurement Games: These games cover how to Estimate Metric Units of Weight and Capacity, Compare Metric Units, Convert Metric Units, Convert Metric Units (Decimal Conversions)


Reading Scales - TransumReading Scales: An activity which checks your ability to read scales in various intervals.


I know it – Third Grade: Scroll down to Measurement (Metric) and select the volume activities. There are similar activities in Fourth Grade and Fifth Grade.



Math is Fun

The Jugs Puzzle: You have 2 jugs of different sizes & an unlimited supply of water. Can you measure the exact amount of water needed? Has six different levels.

IXL | Maths and English Practice

Metric Measures of Volume (capacity): (ie litres and ml) a selection of games from You can do a number of free quizzes each day without having a subscription.


Comparing and converting metric units: Practice games incorporating metric units of mass/weight, capacity and length.

OdlumsOdlum’s Baking with Kids: What better way to develop and perfect your measuring skills! 


Capacity Quiz: (for 6th class) Multiple choice quiz.