Capacity - Measuring the Amount a Container Holds
Capacity is the maximum amount of liquid a container can hold. Every time you fill a glass, measure out medicine, or check how much petrol a car tank holds, you are dealing with capacity.
What Is Capacity?
Capacity describes how much a container can hold, typically for liquids. It is measured in litres and millilitres in the metric system. The key link: 1 ml = 1 cm³, connecting capacity directly to volume.
Metric Units of Capacity
| Unit | Symbol | Relation to 1 litre | Typical use |
|---|---|---|---|
| Millilitre | ml | 1 l = 1,000 ml | Medicines, small drinks |
| Centilitre | cl | 1 l = 100 cl | Wine and spirit bottle labels |
| Decilitre | dl | 1 l = 10 dl | Recipes in some countries |
| Litre | l | Base unit | Milk, juice, water bottles |
Converting Capacity Units
| Conversion | Operation | Example |
|---|---|---|
| l → ml | × 1,000 | 2.5 l = 2,500 ml |
| ml → l | ÷ 1,000 | 750 ml = 0.75 l |
| l → cl | × 100 | 1.5 l = 150 cl |
| cl → ml | × 10 | 25 cl = 250 ml |
Imperial Capacity Units
| Imperial unit | Metric equivalent |
|---|---|
| 1 fluid ounce | ≈ 28.4 ml |
| 1 pint (UK) | 568 ml |
| 1 gallon (UK) | 4.546 l |
| 1 pint (US) | 473 ml |
Worked Examples
Convert 3.2 litres to millilitres.
3.2 × 1,000 = 3,200 ml.
A jug holds 2,400 ml. How many litres is that?
2,400 ÷ 1,000 = 2.4 l.
A fish tank is 60 cm x 30 cm x 40 cm. What is its capacity in litres?
Volume = 60 × 30 × 40 = 72,000 cm³. Since 1 ml = 1 cm³, that is 72,000 ml = 72 litres.
How many 250 ml glasses can be filled from a 2-litre bottle?
2 l = 2,000 ml. 2,000 ÷ 250 = 8 glasses.
Key Takeaways
- Capacity is the maximum amount a container can hold, usually for liquids.
- 1 litre = 1,000 ml = 100 cl.
- 1 ml = 1 cm³ – capacity and volume share this identity.
- UK pint ≈ 568 ml; UK gallon ≈ 4.546 l.
Practice Questions
- Convert 4.75 litres to millilitres.
- A bottle holds 330 ml. How many bottles are needed to fill a 2-litre jug?
- A bath has a capacity of 200 litres. Express this in millilitres.
- A box measures 20 cm x 15 cm x 10 cm. Find its capacity in ml and in litres.
- A recipe needs 3 pints of milk. Approximately how many litres is that?