In this experimentation we are going to prepare the external application as a calendula lotion sample in the proportionate ration of (1: 9) where 1 part is taken as medicine and remaining 9 parts is taken as a vehicle aqueous base and prepared under the UV– visible spectrophotometer to measure their absorbance capacity. This spectrophotometer plays an important role in measurement of quantitative assay in any sample medium. Here we are analysing the absorbance of calendula officinalis mother tincture in mixing with the distilled water in during preparation of external application of aqueous base lotion.