must be less than

USAGE SUMMARY

"must be less than" is correct and can be used in written English.
You can use it to indicate that one value should be smaller than another value. For example, "The temperature in the room must be less than 70 degrees."

✓ Grammatically correct

Academia

News & Media

Science

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

Must be less than one foot tall.

Massachusetts Institute of Technology

o The reporting cycle must be less than one year.

Harvard University

The file size must be less than 10 MB.

Cornell University

Your income must be less than $80,000.

Cornell University

Crucially, the evidence must be less than two years old.

The Guardian

(Sales must be less than half a million).

The New York Times - Arts

Snakes must be "less than six feet long and nonvenomous".

The New York Times

Furthermore, the maximum measurement grid spacing must be less than twice the standoff distance.

Journal of Sound and Vibration

They must be less than monopoly, since that's the highest they could ever be.

Yale University

Your scores must be less than five years old by the time you submit your application.

Harvard University

In most cases, this must be less than £2,657 gross monthly income.

The Guardian

Expert writing Tips

Best practice

When using "must be less than", ensure the units of measurement are clearly defined to avoid ambiguity. For example, specify "must be less than 100MB" rather than just "must be less than 100".

Common error

Avoid using "must be less than" when you intend to include the boundary value. Use "must be less than or equal to" instead to include the limit.

Linguistic Context

The phrase "must be less than" functions as a limiting qualifier. According to Ludwig, the phrase is grammatically correct and can be used in writing to establish an upper boundary or threshold. Many examples in Ludwig show the phrase being used to specify file sizes, income limits, or age restrictions.

Expression frequency: Very common

Frequent in

Science

35%

Academia

30%

News & Media

25%

Less common in

Formal & Business

10%

Wiki

0%

Encyclopedias

0%

Ludwig's WRAP-UP

In summary, the phrase "must be less than" is a grammatically sound and commonly used expression for setting upper limits or restrictions. Ludwig confirms its validity for general use. It frequently appears in academic, scientific, and news contexts. When using this phrase, remember to clearly define the units and to distinguish it from "must be less than or equal to" if the boundary value should be included. By understanding these nuances, you can effectively use "must be less than" in your writing.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

should not exceed

Replaces "must be" with "should not", softening the obligation while retaining the limit.

cannot be greater than

Emphasizes the upper limit using a negative constraint.

has to be smaller than

Uses "has to be" instead of "must be", providing a slightly less formal tone.

needs to be under

Implies a required limit, replacing "less than" with "under".

should remain below

Suggests maintaining a value under a certain level.

is limited to

Focuses on the restriction being imposed on a certain amount.

is capped at

Emphasizes that there is a ceiling or limit.

may not go over

Expresses a prohibition on exceeding a value.

is restricted to

Highlights a restriction imposed on an amount.

cannot surpass

Uses "cannot surpass" to denote that a limit shouldn't be crossed.

FAQs

How do I use "must be less than" in a sentence?

Use "must be less than" to indicate an upper limit that a value cannot exceed. For example, "The file size "must be less than" 10 MB".

What's the difference between "must be less than" and "must be less than or equal to"?

"Must be less than" excludes the specified value as a possibility, while "must be less than or equal to" includes it. For example, if a value "must be less than" 5, it can be 4.99, but not 5. If it "must be less than or equal to" 5, it can be 5.

What can I say instead of "must be less than"?

You can use alternatives like "should not exceed", "cannot be greater than", or "has to be smaller than" depending on the context.

Is "must be lower than" a suitable substitute for "must be less than"?

While "must be lower than" can sometimes be used, it's typically more appropriate when referring to a position or level, such as temperature or altitude. "Must be less than" is more general and applies to quantities.