They run from 8 to 14. Eight is the weakest, and fourteen is the strongest acid there is. To see if a substance is a base, a litmus test may be done. If the test result are blue then the substance is a base. Bases feel soapy and slippery, and in addition to this they have a bitter taste.
Soap is a base.
Neutral substances are those that fall right on the number seven on the pH scale. There are not very many substances that are commonly found to be neutral. The only one is pure water. There is one more way to check the acidity of a substance and this its through litmus paper. If the litmus paper turns red then the substance is an acid, if it turns the paper blue then the substance is a base.