Should Be vs Must Be: Difference and Comparison

The words ‘should be’ and ‘must be’ are stated under modal auxiliaries according to the English language that should be used correctly since a difference between should be and must exists.

Both these words differ in their meaning and characteristics within their form too.

Key Takeaways

  1. Should be implied as a recommendation or suggestion, while it must imply a requirement or obligation.
  2. Should be is used to express the speaker’s opinion, while must be is used to state a rule or law.
  3. It should allow for flexibility and choice while having no room for deviation or negotiation.

Should Be vs Must Be

The term ‘should be’ can be used to suggest something. A person can also use this term to demonstrate his/her opinion. The term ‘must be’ can be used to indicate an action or activity that needs to be done. For example, you must complete your homework today. This shows that the homework needs to be done within the particular time period.

Should Be vs Must Be

‘Should be’ is said to be a modal auxiliary and is used to express the possibility that something could happen in the future. ‘Should be’ is stated as an undesirable goal.


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Should be is used only as a verb, originating from the word ‘sceolde’, an old English term.

‘Must be’ is a modal auxiliary used to express and state a duty to be done or an unavoidable obligation. The word must be used in nearly three contexts with three meanings.

‘Must’ originated from an old English word called ‘Moste’.

Comparison Table

Parameters of comparisonShould BeMust Be
MeaningThis is used to state a person’s obligation or duty in a sentence. This also says what the best thing to do in a specific case in a sentence is.This word states a certainty or a compulsion of something to be done in the present or future in a sentence.
Degree of comparisonWhen this word is used in a sentence, the degree of comparison is relatively low.When this word is used in a sentence, the degree of comparison is the highest.
FunctionStated for giving advice or feedback.Stated that telling something is compulsory to happen.
DerivationIt was derived from the word “sceolde”.It was derived from the word “moste”.
NatureUsually used in informal communication.Usually used in formal or legal communication.

What is Should Be?

A person uses the word should be to state particular duties and obligations. A person also uses ‘should be’ when a thing has to be done in that specific situation only, especially when judging someone’s activities.

Should be’ is used as the past tense of shall be in the future tense. ‘Should be’ is often used to state a piece of advice or a recommendation or talk about something generally said to be right or wrong within certain limits.

There are specific fundamental ways where the word should be is to be used in a sentence.

  1. To tell which is the best choice when something is happening.
  2. If there is a certain chance of something happening.
  3. To give specific or seek a bit of specific advice.
  4. To give and ask a particular reason for something happening.


  1. She should be going to school today since it’s not a holiday.
  2. She should be sleeping early today because she has to wake up early tomorrow.
  3. They should probably drop her home since it’s too late.
  4. I hope I should be reaching on time for the office since the trains are late today.
should be

What is Must Be?

The word ‘must be’ was initially used to express an obligation to do something. This word is used to denote that something is compulsory and it has to happen for sure strongly.

The word must be used as a helping verb in a sentence. This word strongly emphasizes the need for a specific thing to happen in a sentence by stating it.

When a person says it, he means it is a compulsion for something to happen and cannot be unfulfilled.

There are specific essential ways where the word must be is to be used in a sentence.

  1. When a person wants to express a firm action.
  2. When a person states or expresses prohibition of something.
  3. When a person wants to give particular feedback or reviews regarding something
  4. Used in exclamatory sentences.
  5. When a person wants to emphasize strongly that a particular thing has to happen.


  1. This must be so amazing!
  2. You must be kidding.
  3. I must be going, for it is already late.
  4. This dish must be served with ice cream.
  5. The driver must park the car after dropping them off.
must 1

Main Differences Between Should Be and Must Be

  1. The word ‘should be’ denotes the possibility of something happening, whereas ‘must be’ represents certainty.
  2. The term ‘should be’ indicates that something can happen, whereas ‘must be’ suggests something has to occur.
  3. ‘Should be’ is certainly used to give a piece of advice. On the other hand, ‘must be’ denotes a compulsion for something.
  4. The word ‘should be’ is used in an informal conversation, whereas ‘must be’ is used in legal and formal ways.
  5. The degree of emphasizing is more minor in ‘should be,’ whereas the emphasis element is the highest in ‘must be.’
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