The main problem in using hydroxyapatite as implants is its low mechanical resistance. The parameter that defines such characteristic is the elastic modulus, which can be used to evaluate the elasticity that a given sample may support. Elastic modulus is currently obtained by the material’s microhardness data and/or exhausting and indirect procedures, which may lead to low accuracy within the intended estimation range. The aim of this work is to develop a numerical model to predict the elastic modulus of natural hydroxyapatite based on experimental data of samples sintered between 900 and 1300 °C during 1 h in a 2 l/min air flow. The elastic modulus was obtained from nanoindentation measurements. Material consists of less than 37 μm hydroxyapatite powder obtained from fish bones. Samples measuring 10 mm in diameter and 2 mm in thickness were compacted at 350 MPa. The proposed model provides an evaluation of this characteristic with an error of approximately 3.5% when compared to the experimental data.