Must/Have to

What’s the difference between must and have to?

We use must and have to talk about obligation. Have to is generally much more common than must. The meaning of must and have to is similar in positive sentences. However, the negative forms mustn’t and don’t have to have very different uses. Master the difference with Lingolia then put your knowledge to the test in the free exercises.

Example

I know that I must study more if I want to the pass the exam next week.

The teacher told us that we have to study for at least 2 hours every night.

Maria will have to study more than that if she wants to pass.

Last year, she had to hire a tutor to help her pass the exam.

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Must

Obligation from Within

We can use must when the obligation comes from the speaker themselves rather than from an external source.

Examples:
I must study more if I want to pass the exam.
I must stop eating so much sugar.

Future Obligation/Orders

Must doesn’t have a future form. Use will have to to talk about future obligations.

Example:
Shell must have to study more, if she wants to pass the exams next month.

Use must to give orders, instructions or advice for the future.

Example:
The exam starts at 9 o’clock so you must be here by 8:45.

Past Certainty

Use must have + past participle to make deductions or express certainty about something in the past.

Example:
They must have worked hard to get those exam results.

It seems certain that they worked hard.

Have (got) to

Obligation from Outside

To talk generally about external obligations and general responsibilities, we use have to or have got to.

Example:
We’ve got to study every night.
The teacher told us to.
I have to cut sugar out of my diet.
The doctor ordered me to.

There is no difference in meaning between have to and have got to, but note that have got to can only be used in the present tense, while have to cannot be contracted.

Future Obligation/Arrangements

To talk about future obligations use will/going to have to.

Example:
She’ll have to study more if she wants to pass the exams next month.
not: She will have got to study …

For future arrangements use have (got) to.

Example:
I’ve got to help Barry with chemistry tomorrow.

Past Obligation

Use had to to talk about past obligation.

Example:
They had to hire a tutor to help them with Latin.
It was necessary to hire a tutor.

Mustn’t

Use mustn’t when something is not permitted/not allowed by an external source or rule.

Example:
You musn’t use a dictionary during the exam.

You are not allowed to use a dictionary.

Don’t Have to

Use don’t have to when something is optional. There is no negative form of have got to.

Example:
You don’t have to use a dictionary in the exam.
Using a dictionary is not obligatory, but you can use one if you want.