Comparison with as...as

We can show that two things are not equal using not + as + adjective + as
When we use this structure, the first thing mentioned is 'less' than the second thing. The order of the things you are comparing is opposite to that used in comparisons with comparative adjectives.

This one isn't as big as the old one.
(The old one is bigger than this one.)
Jenny's new flat isn't as nice as her old one.
(Jenny's old flat is nicer than her new one.)
Paris isn't as big as Tokyo
(Tokyo is bigger than Paris.)

Contractions
You can contract the subject, the verb to be and not in two ways. There is no difference in meaning:

It isn't as big as...
It's not as big as...

We can use the as....as structure to compare actions. Again, the order of the things compared is the opposite to that in a comparison with comparative adverbs.
It doesn't work as well as we'd hoped.
(We'd hoped it would work better than it does.)
Michael didn't play as well this week as he did last week.
(Michael played better last week than he did this week.)

The as...as structure is often used with quantity expressions such as much and many.
This phone doesn't have as many features as the other one.
(The other phone has more features than this one.)
My ticket didn't cost as much as yours.
(Your ticket cost more than mine.)

We can use not + such + noun phrase + as to compare things using noun phrases.
The journey to London doesn't take such a long time as it used to.
(The journey to London used to take longer.)
I don't have such an interesting job as Julia.
(Julia has a more interesting job than I do.)

When we want to show that there is a big or a small difference between the things being compared we can use the adverbs nearly', nowhere near and quite.

Emphasizing a big difference:
England isn't nearly as big as Russia.
England is nowhere near as big as Russia.
(Russia is much bigger than England.)

My shoes didn't cost nearly as much as yours.
My shoes cost nowhere near as much as yours.
(Your shoes cost much more than mine.)

There aren't nearly as many people here today as there were yesterday.
There are nowhere near as many people here today as there were yesterday.
(There were far more people here yesterday than there are today.)

Setting up a business isn't nearly such a complicated process now as it used to be.
Setting up a business is nowhere near such a complicated process now as it used to be.
(Setting up a business used to be a much more complicated process than it is now.)

Emphasizing a small difference:
My flat isn't quite as big as Jenny's.
(Jenny's flat is a little / a bit / slightly bigger than mine.)
The journey didn't take quite as long as it did last time.
(The journey took a little / a bit / slightly longer last time.)
It isn't quite such a nice restaurant as the one we used before.
(The restaurant we used before was a little / a bit / slightly nicer.)

We can use the as...as structure in a positive form to show that things are the same.
Adjectives
My cooking is as good as yours.
(The quality of my cooking is the same as yours.)
Adverbs
I can sing as well as you can.
(My ability to sing is the same as yours.)
Quantity
There are as many people here who can speak Chinese as English.
(The numbers of people here who can speak Chinese and English are the same.)

When we use nearly and quite to modify positive as...as sentences, the meanings are different.
Small differences: nearly
With a positive as...as structure, nearly shows a small difference
David is nearly as tall as Michael.
(Small difference: Michael is only a little taller than David.)
Compare this with the negative sentence:
David isn't nearly as tall as Michael.
(Big difference: Michael is much taller than David.)

Using quite and just for emphasis
If we want to emphasize that two things are the same, (for example, because the person we are speaking to may not accept what we are saying) we can use
quite and just:

'You're a terrible tennis player!'
'I'm just as good as you!'
This phone is quite as good as that one even if it does cost less.