"I Feel Bad" Is Correct. "I Feel Badly" Usually Is Not. - Grammar Simplified: Master English Rules

Someone says I feel bad about it. Someone else says, kindly, badly. The second person is trying to be helpful and is wrong.

I feel badly means your sense of touch is impaired.

Two jobs a verb can do

Most verbs describe an action. Adverbs modify actions, so an adverb is what follows them: she runs quickly, he writes clearly.

A smaller group of verbs describes not an action but a state. These are linking verbs, and instead of doing something they connect the subject to a description of the subject. What follows is therefore an adjective, because it is describing the subject, not the verb.

She is tired. Not tiredly.
The soup tastes salty. Not saltily.
He seems nervous. Not nervously.
I feel bad. Not badly.

The usual linking verbs are be, become, seem, appear, feel, look, smell, sound, taste, grow, remain, stay, turn.

The complication that causes the confusion

Several of those verbs work both ways, and the meaning changes with the choice.

The dog smelled bad. The dog needed a bath.
The dog smelled badly. The dog had a poor nose.
She looked angry. Her expression was angry.
She looked angrily at the door. She directed an angry look.

In each pair the first sentence uses the verb as a link — describing the subject — and the second uses it as an action, describing how the action was performed. Both constructions are correct. They simply mean different things, and only one of them is usually what you meant.

The substitution test

Replace the verb with a form of be. If the sentence still makes sense, the verb is linking and you want the adjective.

I feel bad → I am bad. Awkward, but structurally sound. Linking verb, adjective.
She looked angrily at the door → She was angrily at the door. Nonsense. Action verb, adverb.

Why so many people believe the opposite

I feel badly is a hypercorrection: an error produced by over-applying a real rule.

Most people are taught, correctly, that adverbs modify verbs and that saying he runs quick is careless. The lesson gets absorbed as a broader instinct: after a verb, use the -ly form. Applied to a linking verb, that instinct produces exactly the wrong answer — and because it feels like the careful choice, it carries an air of authority that the correct version lacks.

The same mechanism produces between you and I, from over-applying the rule about you and me. Hypercorrections are always socially confident, which is what makes them hard to dislodge.

What the authorities say

Merriam-Webster records feel bad as standard and notes that feel badly arose through hypercorrection. Chicago treats bad as the correct complement after a linking verb. There is no authority recommending I feel badly for emotional states.

Usage note: feel badly has become common enough that some dictionaries now record it as an accepted variant in this sense. It is not a hanging offence. But if you are choosing between them, bad is the one with the reasoning behind it.

The pattern to carry away

Ask what the word is describing. If it describes the subject, use an adjective, however verb-like the position looks. If it describes the action, use an adverb.

I feel bad describes me. I feel badly describes my fingertips.