Here, we’re looking at when to use “all of” rather than “all” by itself. Make sure you can avoid errors when using these terms by checking out our guide below.
When to Use “All Of”
The sense of “all” that applies here is its use as a determiner (or a predeterminer). This means using “all” to indicate how much of something we’re discussing. For example, “all students” means “every single student,” not just some of them.
As a rule of thumb, we use “all of” when “all” is a determiner and the next word in the sentence is a pronoun. When this is a personal pronoun (e.g., me, you, us, them) or a relative pronoun (e.g., whom, which), we need the “of” to make the sentence grammatical. For example:
All of you were late to class. ✓
All you were late to class.✗
These are my students, all of whom were late. ✓
These are my students, all whom were late. ✗
When “all” precedes another determiner as part of a noun phrase, though, the “of” is typically optional. This includes the definite article (i.e., the):