Most of you are wrong, since SegWit activation, maximum block size weight limit is 4 million weight unit (not 4MB).
Actual maximum block size depends on the transaction (SegWit or non-SegWit) and how big (in byte) is the signature or/and P2SH size (if transaction use SegWit).
4MB block size is possible, but only under very specific transaction format.
thats the wishy washy code, where devs pretend they have given the community 4mb space. but the reality is expectant to be around 1.2mb-2.1mb average while witness scale factor is limiting utility below 4mb
we still have not surpassed satoshi's 7tx/s calculation (600k tx a day) and he calculated that 8 years ago