Capacity vs Size

When to use each in English, with meaning, register, and examples.

Capacity

Top 2,000 (common)B2noun

Size

Top 1,000 (very common)A2noun
Most common: Size
 CapacitySize
Pronunciation🇬🇧 //kəˈpæs.ɪ.ti//🇺🇸 //kəˈpæ.sɪ.ti//🇬🇧 /["/saɪz/"]/🇺🇸 /["/saɪz/"]/
MeaningHow much something can hold or do.how big or small something is
ExampleThe capacity of the stadium is 50,000 people.The size of the shirt was too small for me.
RegisterNeutralNeutral
How commonTop 2,000 (common)Top 1,000 (very common)
CEFR levelB2A2
Part of speechnounnoun
Collocationsfull capacity, seating capacity, at capacity, capacity limitsconsiderable, enormous, fair, adjust, change, control, grow, increase, decline, from the size of, in size, in the size of, given the size of something, half the size of something, two, three, etc. times the size of something, large, medium, small, range, variety, be, take, wear, fit somebody, in a/​your size, be a size too big, small, etc., size matters
Antonymsinability, incapacitysmall, tiny, minute
Common mistakesConfused with 'capability', which refers to ability rather than volume., Using 'capacity' for individual abilities when 'capability' is more appropriate., Mispronouncing the word with emphasis on the wrong syllable.Confusing 'size' with 'sized'; 'sized' is used as an adjective., Using 'size' where 'amount' would be more appropriate when referring to uncountable quantities., Saying 'the sizes of the shoes' instead of 'the shoe sizes'.
Usage notesUsed in both formal and informal contexts. Common in discussions about limits or ability. Not typically used in casual conversation unless referring to space or limits.Used in both formal and informal contexts. 'Size' is suitable for descriptions of objects, clothing, and measurements but is less appropriate for abstract concepts without clear dimensions.

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Capacity
Size

Frequently asked questions: Capacity vs Size

What's the difference between Capacity and Size?

Capacity: How much something can hold or do. Size: how big or small something is

Which is more common: Capacity and Size?

Size is the most common in everyday English.

Which is more advanced: Capacity and Size?

Capacity is the highest level, at B2, on the CEFR scale.

Are Capacity and Size the same CEFR level?

Capacity: B2, Size: A2 on the CEFR scale.

What part of speech are Capacity and Size?

Capacity: noun, Size: noun.

Can you show an example of each?

Capacity: The capacity of the stadium is 50,000 people. Size: The size of the shirt was too small for me.

Can I use Capacity and Size interchangeably?

Not always. Capacity and Size are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.

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