In this manuscript, fluid dynamics concepts were used to measure the droplet impact velocity and correlate its droplet stain diameter with the velocity and size of the droplet. Experiments were performed to capture videos of droplets dripping at various heights in gravity on different targets. Using the image process, the velocity and diameter of droplets were measured. 50 ml blood was taken from the Indian blood bank, and its viscosity, density, and surface tension were measured by customized lab equipment. Droplet diameter, stain diameter, and droplet impact velocity were measured using the basic concept of fluid mechanics. The analytical formula for knowing the velocity of the impact of droplets on the target was validated against the experimental data. Post-validation stains’ diameter was correlated, and this correlation is useful to the reconstruction of the trajectories of blood drops to find out their point of origin of blood spreading in forensic investigation.