Maths
What is capacity in maths?
Quick answer
Capacity is how much a container can hold, usually measured in millilitres (ml) and litres (l). A large bottle of water often holds 2 litres, which is 2000 ml.
In one sentence
Capacity is the amount a container can hold when it is full, like how much juice fits in a jug.
Explained
A bucket can hold more water than a cup, so the bucket has a bigger capacity. In most of the world, capacity is measured in:
| Unit | Short | Example |
|---|---|---|
| millilitre | ml | a teaspoon is 5 ml |
| litre | l (or L) | 1000 ml, a big carton of milk or juice |
cup
bucket
Converting is just like other metric units: multiply or divide by 1000. 3 l = 3000 ml, and 750 ml = 0.75 l.
Capacity or volume? They are close cousins. Volume is how much space something takes up; capacity is how much a container can hold. A neat link joins them: 1 cubic centimetre (cm³) holds exactly 1 ml, and a 10 cm × 10 cm × 10 cm box holds exactly 1 litre. Amounts of liquid that are actually in a container (not just how much it could hold) are also called volume.
Reading a measuring jug. Put the jug on a flat surface and bend down so your eyes are level with the liquid. Then work out the value of each small mark: if there are 4 spaces between 0 and 200 ml, each space is 50 ml.
Imperial and US units are used for milk, petrol and recipes in some countries:
- US: 2 cups = 1 pint, 2 pints = 1 quart, 4 quarts = 1 gallon. A US cup is about 240 ml.
- UK: 1 pint is about 568 ml, and 8 pints = 1 gallon.
- A UK pint (20 fl oz) is bigger than a US pint (16 fl oz, about 473 ml). So a UK gallon (about 4.55 l) is bigger than a US gallon (about 3.79 l).
Examples
- 2 l = 2000 ml
- 1,250 ml = 1.25 l
- 4 cartons of 250 ml make 1 litre.
- ½ litre = 500 ml; ¼ litre = 250 ml
- A 5 l bucket filled with a 500 ml jug takes 5000 ÷ 500 = 10 jugfuls.
Common mistakes
- Converting by 100. There are 1000 ml in a litre, not 100.
- Reading the jug from above, which makes the level look wrong. Fix: get your eyes level with the line.
- Thinking a taller container always holds more. A tall thin glass can hold less than a short wide bowl. Fix: pour one into the other to check.
Quick quiz
Capacity
Check what you know with 4 quick questions.
Question 1 of 4
How many millilitres are in 1 litre?
Practise it
Try it
Browse maths worksheets for measuring and capacity practice.
For grown-ups
Related topics
Volume
Volume is the amount of space a 3D object takes up, measured in cubic units like cm³ or m³. A box 4 cm by 3 cm by 2 cm has a volume of 24 cm³.
Mass and weight
Mass is how much stuff is in an object, measured in grams and kilograms. Weight is the pull of gravity on that mass. In everyday life people say weight for both.
Length and measuring
Length is how long, tall or far something is. It is measured with a ruler or tape in units such as millimetres, centimetres, metres and kilometres (or inches, feet and miles).
Fractions
A fraction is part of a whole that has been split into equal parts. In ¾, the bottom number says how many equal parts and the top says how many you have.
2D shapes
2D shapes are flat shapes with length and width but no thickness, like circles, triangles, squares and hexagons. You can draw them on paper.
3D shapes
3D shapes are solid shapes with length, width and height, like cubes, spheres, cylinders and pyramids. They have faces, edges and vertices.