Who vs Whom: which is correct?

Subject versus object, made concrete

Who and whom are the question-and-relative versions of the difference between he and him, or she and her. Who is the subject form: it does the action. Whom is the object form: it receives the action or follows a preposition. Who called the meeting? (who is doing the calling). Whom did you invite? (whom is being invited, the object of invite). The grammar is identical to choosing between he and him; only the words look more intimidating.

That similarity is the basis of the only test you need. Reword the sentence as a plain statement and answer it with he or him. If the natural answer uses he (or she, they), the right choice is who. If the answer uses him (or her, them), the right choice is whom. The memory hook is that whom and him both end in m, so him answers point to whom.

The he/him test, step by step

Take the question Who/whom should I call? Turn it into a statement and answer it: I should call him. The answer is him, ending in m, so the word is whom: Whom should I call? Now try Who/whom is responsible? Answer: he is responsible. The answer is he, so the word is who: Who is responsible?

For relative clauses, the same test works on the clause alone. In the candidate who/whom we hired, isolate we hired ___ and fill the blank: we hired him. Him, so whom: the candidate whom we hired. In the candidate who/whom impressed us, isolate ___ impressed us: he impressed us. He, so who: the candidate who impressed us. Splitting a long sentence down to the small clause that contains who or whom makes the test easy even when the sentence is complicated.

Prepositions are the clearest case of all. After to, for, with, from, by, and about, the object form is almost always required: to whom, for whom, with whom, from whom. The bell tolls for whom, you can rely on whom, the person about whom we spoke. If a preposition sits right before the word, whom is nearly always correct.

When whom is genuinely optional

Modern English is relaxing about whom, especially at the start of a question. Who did you call? is now widely accepted in speech and informal writing even though whom is strictly correct, because starting a sentence with Whom can sound stiff. In casual contexts, choosing who there will rarely be marked as wrong, and many style guides accept it.

Whom remains expected in two situations: directly after a preposition (to whom, with whom), where Who do you wish to speak to? feels noticeably looser than To whom do you wish to speak?; and in formal writing such as academic papers, legal documents, and professional correspondence, where the correct object form signals careful prose. So the practical rule is: use the he/him test to know which is technically correct, then keep whom after prepositions and in formal registers, and feel free to relax to who in casual speech and chat.

Building the habit

Because the he/him test is mechanical, the path to confidence is simply running it until it becomes instant. When you draft, do not agonise; when you edit, find each who or whom, reduce the sentence to its core clause, and answer with he or him. The m of him matches the m of whom. That is the entire method, and it never gives a wrong answer.

Avoid the trap of adding whom just to sound educated. Hypercorrection, writing whom where who belongs because whom feels fancier, is a common and noticeable error: a person whom is kind is wrong, because the test gives he is kind, so it must be a person who is kind. Trust the test over the instinct to sound formal. Practise on the quiz above, which mixes subjects, objects, relative clauses, and prepositions, and the choice will start to feel as natural as choosing between he and him already does.