Amount vs. Number
Use “amount” with uncountable nouns and “number” with countable plural nouns. The distinction depends on whether you are measuring a mass or quantity that is not normally counted as separate units, or counting individual items.
Use “amount of” with uncountable nouns such as time, water, or traffic. Use “number of” with countable plural nouns such as emails, people, or mistakes.
Key details
Choose the right form
| Noun type | Choose | Example |
|---|---|---|
| Uncountable/mass noun | amount of | amount of water / amount of time |
| Countable plural noun | number of | number of emails / number of people |
| Informal countable use with “amount” | possible in speech, but avoid in edited standard prose | Prefer “number” when individual items are countable. |
Quick tests
Countability test
Can you normally count the noun as one, two, three individual items and form a plural?
If yes: Use “number of.”
If no: Use “amount of” for an uncountable quantity.
Caveat: Some nouns can be countable in one meaning and uncountable in another, so test the noun as it is used in the sentence.
Examples
A large number of applications arrived on Monday.
“Applications” are countable individual items.
We spent a large amount of time reviewing them.
“Time” is treated as an uncountable quantity here.
Further guidance
Common Trap
Informal speech sometimes uses “amount of” with countable nouns, but edited standard English generally prefers “number of” when the noun is countable.
Core Rule
Cambridge Grammar distinguishes “amount of” for uncountable nouns from “number of” for countable nouns.
Countability Test
Ask whether the noun normally forms a plural that you can count one by one. If yes, “number of” is normally the standard choice; if not, “amount of” is normally appropriate.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Amount of, number of or quantity of? — Cambridge Grammar (opens in a new tab)Cambridge University Press · Countability rule for amount of and number of