Testing cotton strength requires combined measurements of tensile force and specimen mass. Both light attenuation and air flow measurements of mass used by HVI systems are adjusted for level differences caused by fiber fineness. Presently the adjustment is made with a micronaire reading which does not accurately represent the fineness of some cottons. Cut-and-weight methods were used to compare the actual fineness of HVI bundles with micronaire values. Mass measuring errors were estimated from HVI correction equations. Among thirty-five varieties surveyed the average error was 2.99% for air flow methods and 4.11% for light attenuation methods.