Check if file size greater than a small number?

[Peng Yu]

https://stackoverflow.com/questions/5920333/how-can-i-check-the-size-of-a-file-using-bash

I see things like the above that call an external program or cat all
the file content to check the size of a file.

But if my goal is just to know whether the file size is greater than a
smaller (say 40). What is the most efficient way to do so in bash?

-- 
Regards,
Peng