Year 5 maths · Key Stage 2 · Measurement

Year 5 measurement: units, perimeter, area and volume

Year 5 measurement pulls together a lot of earlier number work. Children convert between metric units, learn rough equivalents for inches, pounds and pints, and find the perimeter of shapes made from rectangles. They calculate area in square centimetres and square metres, estimate volume and capacity, convert between units of time, and solve money and measure problems with decimals.

Units, perimeter, area and volume, explained

Converting metric units is multiplication and division by 10, 100 and 1,000. There are 1,000 m in a kilometre, 100 cm in a metre, 10 mm in a centimetre, 1,000 g in a kilogram and 1,000 ml in a litre. Changing to a smaller unit gives a bigger number, so 2.4 km is 2,400 m, while changing to a larger unit gives a smaller one, so 3,500 g is 3.5 kg. Children also learn rough equivalents between metric and imperial units. Schools often use 1 inch ≈ 2.5 cm, 1 kg ≈ 2.2 pounds and 1 pint ≈ 570 ml, and the point is to make sensible estimates, not exact conversions.

Perimeter is the distance around the edge of a shape. For rectilinear shapes, which have only straight sides and right angles, such as an L-shape, children add every side and work out any missing lengths by subtracting from the sides they know. They also work backwards: a rectangle with a perimeter of 20 cm and a length of 6 cm has a width of 4 cm, because the two lengths and two widths must total 20 cm. Area is the amount of surface covered, in square centimetres (cm²) or square metres (m²). For a rectangle, multiply the length by the width. Comparing areas shows that perimeter and area are different things: a 5 cm by 5 cm square and a 9 cm by 1 cm rectangle both have a perimeter of 20 cm, but their areas are 25 cm² and 9 cm². For an irregular shape, such as a hand drawn round, children estimate by counting squares, treating part squares as whole when they are about half full or more.

Volume is the amount of space a solid takes up, and capacity is how much a container holds. In Year 5 the focus is on estimating. Children build cuboids from 1 cm³ blocks and count them, and use litres and millilitres to describe how much a jug, bottle or bath holds, often by pouring water. The formula length × width × height is a Year 6 topic, and Year 5 is about the idea that volume counts cubes, not squares.

Measure and money problems use all four operations, often with decimals: four parcels of 1.25 kg weigh 5 kg, and 3 m of ribbon at £0.80 a metre costs £2.40. Scaling comes up when a recipe is doubled or halved, or when lengths are read from a scale drawing. Children also convert between units of time, such as seconds, minutes, hours, days, weeks, months and years: 135 minutes is 2 hours 15 minutes, and 23 days is 3 weeks and 2 days. Time doesn’t work like decimals, because an hour has 60 minutes, not 100.

Words your child will hear

Perimeter: The total distance around the outside of a shape.
Area: The amount of flat surface a shape covers, measured in square units such as cm² or m².
Volume: The amount of space a solid takes up, measured in cubic units such as cm³.
Capacity: How much a container can hold, usually in litres (l) or millilitres (ml).
Rectilinear: Made up of straight sides that meet at right angles, such as an L-shape.
Metric and imperial: Metric units (metres, kilograms, litres) are based on tens, hundreds and thousands. Imperial units (inches, pounds, pints) are older units still used in everyday life.
Convert: Change a measurement from one unit to another, such as kilometres to metres.

What the National Curriculum says

In Year 5, pupils should be taught to:

Convert between different units of metric measure [for example, kilometre and metre; centimetre and metre; centimetre and millimetre; gram and kilogram; litre and millilitre]
Understand and use approximate equivalences between metric units and common imperial units such as inches, pounds and pints
Measure and calculate the perimeter of composite rectilinear shapes in centimetres and metres
Calculate and compare the area of rectangles (including squares), including using standard units, square centimetres (cm²) and square metres (m²), and estimate the area of irregular shapes
Estimate volume [for example, using 1 cm³ blocks to build cuboids (including cubes)] and capacity [for example, using water]
Solve problems involving converting between units of time
Use all four operations to solve problems involving measure [for example, length, mass, volume, money] using decimal notation, including scaling

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

A worked example

A rectangular patio is 9 m long and 6 m wide. A square 2 m by 2 m is left out of one corner for a tree. What are the perimeter and the area of the patio?

Sketch the shape and label it. Going round the outside, the sides are 9 m along the bottom, then up 4 m (6 − 2), across 2 m, up 2 m, back across 7 m (9 − 2) and down 6 m.
```
9 + 4 + 2 + 2 + 7 + 6
```
Add the sides to find the perimeter.
```
9 + 4 + 2 + 2 + 7 + 6 = 30 m
```
Check with a shortcut. Cutting a square out of a corner leaves the perimeter of the original rectangle unchanged, because the two short sides of the notch replace two sides of the same length. 9 + 6 + 9 + 6 = 30 m.
For the area, find the area of the whole rectangle and take away the corner that is missing.
```
9 × 6 = 54 m²
2 × 2 = 4 m²
54 − 4 = 50 m²
```
Write the units. Perimeter is a length, so it is in metres. Area is a surface, so it is in square metres.

The perimeter is 30 m and the area is 50 m².

Common mistakes and how to help

Mixing up perimeter and area

Both come from the same rectangle, and both involve its side lengths. A child adds when the question asks for area, or multiplies when it asks for perimeter.

What helps: Link each to something real: perimeter is the fence around the edge (a length), area is the grass inside (a surface, in squares). Always check the units: m for perimeter, m² for area.

Converting the wrong way

A child changes 2.4 km to 2.4 ÷ 1,000 = 0.0024 m, because they know “you divide by 1,000” but not when to do it.

What helps: Ask whether the answer should be a bigger or smaller number. A kilometre is far longer than a metre, so 2.4 km needs lots of metres. Smaller unit, bigger number.

Treating time as if it were decimal

1 hour 45 minutes is written as 1.45 hours, or 2.5 hours becomes 2 hours 50 minutes. Everything else in Year 5 measure is based on tens, so time feels like it should be too.

What helps: Use a clock face. Half an hour is 30 minutes, so 2.5 hours is 2 hours 30 minutes. Convert everything to minutes before adding or subtracting.

Missing out the unlabelled sides of an L-shape

Only the sides with numbers on are added, so the perimeter is too small. Some lengths have to be worked out from the others.

What helps: Count the sides first and tick each one off as you add it. Work out each missing length by comparing opposite sides: in the patio, the 2 m and 7 m sides across the top must add up to the 9 m side across the bottom.

How to help at home

Compare units in the kitchen. Weigh ingredients in grams and kilograms, and read a milk or squash label that shows both millilitres and pints. Ask: “If a pint is about 570 ml, is a 2-litre bottle more or less than 3 pints?”
Find the area of a room, rug or table. Measure a rug in metres and multiply, or count floor tiles. Draw round your hand on squared paper and estimate its area by counting squares, treating part squares sensibly.
Build cuboids with bricks. Use dice, sugar cubes or identical cube-shaped bricks and ask your child to make a cuboid, count the cubes in it, and then guess how many it would take to fill a small box. Counting the cubes shows what volume means.
Plan journeys with time. Ask how long a journey takes if you leave at 9:50 and arrive at 11:15, or how many weeks and days there are until a birthday. Converting between hours and minutes, and days and weeks, is everyday practice.
Pour and estimate capacity. Under adult supervision, guess how many cups or spoonfuls fill a jug, then check by pouring. Record the answers in millilitres and litres and convert between them.

Builds on

Year 4: Area, perimeter, units and time

Leads on to

Year 6: Units, area and volume

Everything in Year 5 maths

Updated 20 October 2026.