ZnO nanoparticles were synthesized by coprecipitation at 450°C and characterized by XRD and TEM. XRD results showed a wurtzite structure, while TEM revealed spherical particles with an average size of 50 nm. The Williamson-Hall (W-H) analysis was used to estimate crystallite size and lattice strain. The analysis involved different models: uniform deformation model (UDM), uniform deformation stress model (UDSM), and uniform deformation energy density model (UDEDM). The results showed that the three models yield different strain values due to the anisotropic nature of ZnO. The average crystallite size calculated from TEM, Scherrer's formula, and W-H analysis was highly intercorrelated. The root mean square strain was determined from interplanar spacing and strain from the three models. The W-H analysis was found to be effective in estimating crystallite size and lattice strain. The results showed that the crystallite size calculated from the W-H analysis was in agreement with that from TEM. The study highlights the importance of W-H analysis in determining the crystallite size and lattice strain of ZnO nanoparticles. The results also indicate that the three models are suitable for evaluating the crystallite size of ZnO nanoparticles. The study concludes that the W-H analysis is a reliable method for estimating the lattice strain and crystallite size of ZnO nanoparticles.ZnO nanoparticles were synthesized by coprecipitation at 450°C and characterized by XRD and TEM. XRD results showed a wurtzite structure, while TEM revealed spherical particles with an average size of 50 nm. The Williamson-Hall (W-H) analysis was used to estimate crystallite size and lattice strain. The analysis involved different models: uniform deformation model (UDM), uniform deformation stress model (UDSM), and uniform deformation energy density model (UDEDM). The results showed that the three models yield different strain values due to the anisotropic nature of ZnO. The average crystallite size calculated from TEM, Scherrer's formula, and W-H analysis was highly intercorrelated. The root mean square strain was determined from interplanar spacing and strain from the three models. The W-H analysis was found to be effective in estimating crystallite size and lattice strain. The results showed that the crystallite size calculated from the W-H analysis was in agreement with that from TEM. The study highlights the importance of W-H analysis in determining the crystallite size and lattice strain of ZnO nanoparticles. The results also indicate that the three models are suitable for evaluating the crystallite size of ZnO nanoparticles. The study concludes that the W-H analysis is a reliable method for estimating the lattice strain and crystallite size of ZnO nanoparticles.