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Prepositions after adjectives

Unsure of vs. unsure about

Both unsure of and unsure about are standard. Of is often used with facts or answers, while about is common for broader topics or decisions.

Quick answer

Which is correct: unsure of or unsure about?

Both forms are correct. Use unsure of for a specific fact, person, or outcome, and unsure about for a topic, plan, or decision. In many cases, either can work.

I'm unsure of the address.
She's unsure about moving abroad.
They were unsure of the results.
He felt unsure about the proposal.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
unsure of + fact/detail

Not certain about specific information

Use unsure of with facts, names, answers, or outcomes.

I'm unsure of the exact date.
She was unsure of his intentions.
2
unsure about + topic/decision

Expressing uncertainty about a situation

Use unsure about for broader subjects, choices, or plans.

They're unsure about the merger.
He is unsure about studying abroad.
3
unsure whether + clause

Introducing alternatives or uncertainty

Whether is common before a full clause.

I'm unsure whether we should continue.
4
unsure how + clause

Expressing uncertainty about method

Use how before a clause about method or process.

She was unsure how to respond.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
unsure of
I'm unsure of the answer.
uncertainty about a specific fact or thing
unsure about
He's unsure about the new policy.
uncertainty about a broader issue or decision
unsure whether
They were unsure whether to stay.
introduces alternatives or doubt
unsure how
She felt unsure how to begin.
uncertainty about method or action

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using unsure for certainty

Unsure means not certain.

✕ I'm unsure that this is definitely correct. ✓ I'm not sure that this is definitely correct.

Confusing of and about

Of often sounds better with precise details.

✕ I'm unsure about his phone number. ✓ I'm unsure of his phone number.

Missing a preposition

Unsure usually needs of or about before a noun phrase.

✕ She is unsure the plan. ✓ She is unsure about the plan.

Using unsure with an infinitive directly

Use whether or how before clauses.

✕ They were unsure to continue. ✓ They were unsure whether to continue.

Quick practice

Choose the expression that matches the intended meaning.

1. I'm unsure ___ the meeting time.
2. She feels unsure ___ changing careers.
3. They were unsure ___ to accept the offer.

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Frequently asked questions

Are unsure of and unsure about interchangeable?

Often yes, but of is more common with precise facts and about with broader issues.

Can I say unsure whether?

Yes. Unsure whether is very common before a clause.

Is not sure more common than unsure?

In everyday conversation, not sure is often more natural and informal.

ubiquitous in, on, across, throughout or for? "ugly in", "ugly for" or "ugly of"? ultimate in, of, for, on or as? "unacceptable to", "unacceptable in" or "unacceptable for"? unaccounted for unaccustomed to or in? unacquainted with unaffected by, in, for or with? "unaffordable for" or "unaffordable to"? unanimous in, on, about, regarding or for? "unattractive to" or "unattractive for"? "unavailable for" or "unavailable to"?

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