This chapter basically talks about the learning basic mathematics. Learning calculation of drug dosage will help nurses to solve dosages problem easily and will build-up their confidence for administering drug safely. This chapter provides the detail about the whole numbers, fraction, parts of fraction, types of fraction, reducing fraction, mixed number, lowest common denominator, addition and subtraction of fractions, multiplication of fractions, division of fractions, ratio, proportion, linear ratio and proportion, fractional ratio and proportion, decimal number, which are discussed with the help of examples.