[en] Studies of nuclear reactions relevant to astrophysical scenario, often require measurement of cross-section in pico-barn to nano-barn range (1 barn = 10^-24 cm²). So isotopically pure targets are needed and the thickness of the target should be known accurately. In nuclear structure experiment also, target thickness information is very important to estimate the reaction rate as well as the level lifetimes. In the present work, the X-ray Fluorescence technique has been used to measure the target thickness. The concept of attenuation of fluorescence X-ray of the backing material has been used