Although it is true that cucumbers tend to be much larger than pickles, that is not always the case. Sometimes you will find that certain pickles grow abnormally large and are therefore as big or larger than the average cucumber. Because there are a few different types of pickles, it depends on which ones you are referring to when comparing sizes of the pickle and the cucumber.
Typically cucumbers are anywhere from seven to ten inches in length, whereas most pickles are only about five to six inches in length. Cucumbers also tend to be much thicker than pickles in general.