Aim: To calibrate UV–Visible spectrophotometer. Theory: The Ultra–Violet (UV) and visible spectroscopy is also known as Electron spectroscopy because it involves the promotion of electrons from ground to higher energy states. The electronic excitation occurring in the range of 190–800 nm wavelengths is studied in Ultra–Violet and visible spectroscopy. Since, the energy levels of the molecules are quantized, thus the energy required to bring about the excitation of the electrons is established. This leads to the fact that the electromagnetic radiations of only fixed frequency will cause excitation.