Whoever and whomever fulfill roles similar to the ones that who and whom do. Whoever functions as a subject and whomever as an object. In fact, the same substitution trick used for who/whom also works for whoever/whomever. If you can substitute he/she, you should use whoever. If you can substitute him/her, go with whomever.
However, sentences using whoever/whomever are generally more advanced than those which simply use who/whom. Keep the following in mind when trying to decide between whoever and whomever.
“Whoever/whomever” = Dependent Clause
Any sentence that requires you to make a whoever/whomever decision will contain a dependent clause. Whoever/whomever should agree with the verb within that dependent clause, not with the main verb of the sentence as a whole:
The board will promote whomever Gerald recommends.
Whomever is correct in this instance because you wouldn’t say “Gerald recommended he/she.” Instead, you would say “Gerald recommended him/her.”
The board will promote whoever is the most experienced.
Because “he/she is the most experienced” is grammatically correct, whoever is also the correct choice in this situation.
“Whoever/whomever” Clauses as the Subjects of Sentences
A clause containing whoever/whomever can function as the subject of a sentence. Because the entire clause is the subject of the main verb, you will need to look inside the clause itself to determine whether you should use whoever or whomever:
Whoever is hired will complete a three month probationary period.
The clause “whoever is hired” is the subject of “will complete.” “Whoever” is the subject of “is hired” within the clause. Let’s double check this with the he/him trick:
He is hired. – Correct
Him is hired. – Incorrect
Whomever you hire will complete a three month probationary period.
While “whomever you hire” is still the subject of “will complete” in this example, “whomever” is now the object of “hire.” Don’t let the word order fool you. If we perform the he/him trick on this example, we’ll see that “whomever” is indeed correct:
You hired him. – Correct
You hired he. – Incorrect
When possible, you should rewrite sentences to avoid having to make the whoever/whomever choice in the first place. Here are versions of two of the sample sentences in this lesson that sidestep the decision altogether:
The board will promote the most experienced employee.
The person you hire will complete a three month probationary period.