Automated and manual methods to quickly and inexpensively estimate the moisture content of universal density cotton bales were developed. As a basis for the methods, new mathematical relationships describing the force required to compress cotton were developed to focus on moisture content. Implementation of these relationships requires values for press volume and pressure at the end of the compression cycle as well as cylinder diameter and bale weight. The automated method is computer-based whereas the manual method is based on retrofitting a traditional hydraulic pressure gauge with a specially configured dial face. Bale moisture is estimated within ± 0.5%. The devices provide inexpensive methods to estimate the moisture content of cotton bales.