Objective: To develop a simplified algorithm for determining the size and shape of the silver nanoparticles (AgNP) from Electron microscopic (EM) images using MATLAB. Method: We examined the particle size of AgNP from the Transmission electron microscopic and Scanning electron microscopic image with uneven background. This approach based on image processing techniques in MATLAB. Results: The user friendly Graphical User interface (GUI) tool was developed using MATLAB to measure the size of every particle from EM image. The mean particle size of AgNP calculated using this GUI tool by analyzing the N number of particle in the image. Conclusion: This algorithm allows to measure the size of nanoparticles successfully were difficult to analyse by electron microscope with lack of in-built software. The step by step process leads to optimize the process of nanoparticles synthesis and facilitate to generate the needed statistical analysis for medical and other applications.