To calculate the error in density for a cylinder, the mass, diameter, and height must be considered along with their respective uncertainties. The discussion highlights the importance of using the product rule for error propagation, which combines relative errors of the measurements. There is a debate on whether to add errors linearly or quadratically, with one participant noting that linear addition is a more conservative approach. The conversation also emphasizes the need for clarity in posts, as one user failed to provide a complete question or solution attempt. Understanding these error calculation methods is crucial for accurate density determination.