Taylor dispersion is capable of measuring accurately the hydrodynamic radius over several orders of magnitude. Accordingly, it is now a highly competitive technique dedicated to characterizing small molecules, proteins, macromolecules, nanoparticles, and their self-assembly. Regardless, an in-depth analysis addressing the precision of the technique, being a key indicator of reproducibility, is not available. Benefiting from analytical modeling and statistical analysis, we address error propagation and present a comprehensive theoretical study of the precision of Taylor dispersion. Theory is then compared against experiment, and we find full consistency. Our results are most helpful when the design, objectives, or control of analytical quality is in focus.