Is there a specific measure for impurity?

The basic principle regarding things is purity. Nothing is ruled ritually impure except with evidence from the Quran, Sunnah, or the consensus of the early Muslim generations. Evidence has shown the ritual impurity of urine, feces, pre-seminal fluid (madhy), menstrual blood, carrion, pig's blood, dog's saliva, donkey's dung, and intoxicants (khamr). Some impurities may be excused in certain circumstances, such as a small amount of blood. A Muslim should not open the door to obsessive doubts (waswas).