Differentiate between the use of must and have to.

What is the difference between need to and have to?

MUST

To show certainty	To show a necessary condition	To make a strong recommendation
Mother said that she would be back by six. She must be the one knocking on the door.	You must study really hard to clear the entrance exams.	You must try on this new shirt. It is the new look of generation next.

'Have to' similar to 'must'.

'Have to' is used to denote strong obligation or responsibilities. If the obligation depends upon external circumstances, then we use 'have to'. In more personal cases, we use 'must'.

You must study tomorrow. (more personal)
I have to reach office at 8. 

There is hardly any difference between them.

'Need' is used to denote an action that should be done.

You need to wash your dirty clothes.