Year 3 measurement: length, mass, capacity, money and time

Length, mass, money and time, explained

The metric units children use are metres, centimetres and millimetres for length; kilograms and grams for mass; and litres and millilitres for capacity. They know that 1 m is 100 cm, 1 cm is 10 mm, 1 kg is 1,000 g and 1 l is 1,000 ml, and use these facts with whole numbers, for example 5 m = 500 cm. They read rulers, scales and jugs where the marks fall between numbers, working out what each small division is worth. Then they compare and calculate: 1 kg 200 g plus 350 g, or a rope that is 3 times as long as one of 40 cm.

Perimeter is the distance all the way around the edge of a flat shape. Children measure each side of simple 2-D shapes with a ruler and add the lengths. It is most useful to start with a real shape, such as a book cover or a picture frame, so the idea of walking round the edge is clear before any numbers appear.

With money, children add and subtract amounts, and give change, using pounds and pence in practical situations such as a pretend shop. They record pounds and pence separately, for example £2 and 45p; writing money as a decimal, like £2.45, comes in Year 4. Change is often found by counting on from the price up to the amount paid, which is usually easier than subtracting.

Time has the most to learn. Children tell and write the time from an analogue clock, including clocks with Roman numerals from I to XII, and from digital clocks, first on the 12-hour clock and then on the 24-hour clock, so that 15:00 is 3 pm. They estimate the time and then read it to the nearest minute, and use the words o’clock, am, pm, morning, afternoon, noon and midnight. They also learn there are 60 seconds in a minute and 60 minutes in an hour, and record and compare times in seconds, minutes and hours, for example timing how many seconds it takes to write their name.

Children learn the number of days in each month, and that a year has 365 days while a leap year has 366, with an extra day on 29 February. A rhyme or counting along the knuckles of a fist is a favourite way to remember the months. Finally they compare how long things take, working out the duration of an event from its start and finish times, which is the hardest part because time doesn’t work in tens.

Words your child will hear

Perimeter

The total distance around the outside edge of a 2-D shape.

Capacity

How much a container can hold, measured in litres and millilitres.

Mass

How much matter something contains, which we measure by weighing in grams and kilograms.

Duration

How long something lasts, such as 45 minutes.

am and pm

am is from midnight to noon and pm is from noon to midnight.

24-hour clock

A clock that counts the hours from 00 to 23, so 3 pm is 15:00.

Leap year

A year with 366 days, with 29 days in February. It usually comes round every four years.

What the National Curriculum says

In Year 3, pupils should be taught to:

• Measure, compare, add and subtract: lengths (m/cm/mm); mass (kg/g); volume/capacity (l/ml)
• Measure the perimeter of simple 2-D shapes
• Add and subtract amounts of money to give change, using both £ and p in practical contexts
• Tell and write the time from an analogue clock, including using Roman numerals from I to XII, and 12-hour and 24-hour clocks
• Estimate and read time with increasing accuracy to the nearest minute; record and compare time in terms of seconds, minutes and hours; use vocabulary such as o’clock, am/pm, morning, afternoon, noon and midnight
• Know the number of seconds in a minute and the number of days in each month, year and leap year
• Compare durations of events [for example, to calculate the time taken by particular events or tasks]

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

A worked example

Common mistakes and how to help

How to help at home

• Measure in the kitchen. Weigh ingredients on kitchen scales and pour liquids into a jug, asking your child to read the scale between marks. “Is this more or less than half a litre?” builds a sense of size.
• Find the perimeter of something real. Measure the edges of a table mat, a picture frame or a rug with a tape measure and add them up. Ask first for an estimate, then measure and see how close it was.
• Play shops with real coins. Price a few items between 20p and £5 and pay with a bigger coin or note. Your child counts on from the price to find the change, saying each step aloud.
• Talk about time as you go. Keep an analogue clock where your child can see it. “It’s 4:10. We leave at 4:45. How long have we got?” turns durations into everyday practice.
• Use a calendar. Count the days until a birthday or a holiday, and work out which months have 30 days, 31 days or fewer. Look at February together and talk about why it has 29 days in a leap year, such as 2028, and 28 days in other years.

Related topics

Everything in Year 3 maths