This study investigates the synthesis of nano-crystalline hydroxyapatite (HAp) using wet chemical precipitation in different organic media, including mustard oil, soybean oil, and coconut oil. X-ray diffraction (XRD) analysis confirmed the crystalline phase of HAp in all media, aligning with standard databases. Various models, such as the Scherrer's Method (SM), Halder-Wagner Method (HWM), linear straight-line method (LSLM), Williamson-Hall Method (WHM), Monshi-Scherrer Method (MSM), Size-Strain Plot Method (SSPM), and Sahadat-Scherrer Method (S-S), were applied to determine the crystallite size. The stress, strain, and energy density were also computed from these models. The calculated crystallite sizes ranged from 6.5 nm for HAp in mustard oil using the Halder-Wagner method to 143 nm for HAp in coconut oil using the Scherrer equation. The Williamson-Hall model provided the most accurate crystallite size, stress, and strain values, with crystallite sizes below 150 nm for all samples, except for the linear straight-line method, which resulted in a significantly larger size of 693.27 nm for pure HAp and 13865.4 nm for mustard oil. The study highlights the effectiveness of the Williamson-Hall model in accurately estimating the crystallite size and elastic properties of HAp synthesized in different organic media.This study investigates the synthesis of nano-crystalline hydroxyapatite (HAp) using wet chemical precipitation in different organic media, including mustard oil, soybean oil, and coconut oil. X-ray diffraction (XRD) analysis confirmed the crystalline phase of HAp in all media, aligning with standard databases. Various models, such as the Scherrer's Method (SM), Halder-Wagner Method (HWM), linear straight-line method (LSLM), Williamson-Hall Method (WHM), Monshi-Scherrer Method (MSM), Size-Strain Plot Method (SSPM), and Sahadat-Scherrer Method (S-S), were applied to determine the crystallite size. The stress, strain, and energy density were also computed from these models. The calculated crystallite sizes ranged from 6.5 nm for HAp in mustard oil using the Halder-Wagner method to 143 nm for HAp in coconut oil using the Scherrer equation. The Williamson-Hall model provided the most accurate crystallite size, stress, and strain values, with crystallite sizes below 150 nm for all samples, except for the linear straight-line method, which resulted in a significantly larger size of 693.27 nm for pure HAp and 13865.4 nm for mustard oil. The study highlights the effectiveness of the Williamson-Hall model in accurately estimating the crystallite size and elastic properties of HAp synthesized in different organic media.