How to tell how many gb my iPhone 4has?

How to tell how many gb my iPhone 4has?

Front toward enemy.

Look in your settings and there should be a storage option

Settings>General>About>Capacity
That'll tell you the maximum amount of gigabytes that are available to you, the user. Available is how much you have left.

Could plug into a computer & check through iTunes
or on the phone check Settings > General > About & you'd see it there (though keep in mind it would say a figure close to 16, 32 not exactly that)