Informally, if and whether can be interchanged. However, in formal writing, it pays to know the distinct uses of each. As a general rule, use if in conditional sentences. Use Whether to present two possible alternatives.

Uses of If and When

• We can use If and Whether in indirect questions. Use if or whether for indirect yes-no questions and questions with or. If is more commonly used than whether.

Call the parents and find out if any of them can volunteer for the cleanup drive.

I talked to him and asked if he’d take a taxi or if he’d drive from the airport.

• With or, it is more common to use whether especially when two or more alternatives in the indirect question are available.

After the class, the students asked whether they should take an exam, make a book report, or both.

• In more formal context, we use whether.

The suspect will be asked whether he would confess to his crime.

• From a business meeting, notice whether being used.

Carrie read an article that she’d written and the executives decided whether it should be published.

• Use or not with if and whether when talking about an alternative. Put or not immediately after whether or at the end. With if, only use or not in end position.

They texted Michelle to confirm whether or not she really got sick.

I texted Chase to confirm whether he really got sick or not.

He texted Angel to find out if she really got sick or not.

• To introduce clauses that comes after verbs that express doubts, use if or whether.

She isn’t sure if she can sleep. She’s too excited.

I didn’t study properly so I doubt if I’m going to pass the test.

We’re not sure whether we’ll be able to call you from the village.

Uses of Whether

• To talk about future plans or decisions, use whether before a to-infinitive.

She was thinking whether to study English abroad.

Some household chores, such as cleaning, need to be done by every member. Others, such as whether to iron clothes, can only be done by just one person.

• Use whether after prepositions.

Correct: I don’t think she worries about whether you are happy or not.

Incorrect: I don’t think she worries about if you are happy or not.

Common Mistakes in Using If and Whether

• Using if before a to-infinitive

Correct: He doesn’t know whether to save his money or just save it.

Incorrect: He doesn’t know if to save his money or just save it.

• Using if directly before or not

Correct: Can you tell me whether or not you are available for an interview?

Incorrect: Can you tell me if or not you are available for an interview?

• Using if after prepositions

[talking about a trip to Australia for a year]

Correct: They are not sure about whether they get good jobs after graduation. They just want to finish their degrees as soon as possible.

Incorrect: They are not sure about if they get good jobs after graduation. They just want to finish their degrees as soon as possible.