Density is one of the essential characteristics of composite propellants. A common method for estimating the density of materials is hydrostatic weighing, which is based on Archimedes’ principle. The technique, often known as underwater weighing, may also be used to determine the density of composite propellants, which are categorized as porous solid materials. Although the method is simple, the stability issue of water weighing needs to be considered since the propellant's component may dissolve in water. This work investigates the impact of hydrostatic weighing immersion time on the density of an AP-based composite propellant. It was done by adjusting the immersion time of samples to assess propellant density and comparing the result with the theoretical value. The study found that the loss of density value and accuracy increased with immersion time. Setting the immersion times below five minutes is recommended to achieve the density value with more than 99% accuracy.