Presence of non-lint materials (trash) in commercial cotton bales at various amounts degrades market values and further influences end-use qualities. To ensure fair trading, the USDA Agricultural Marketing Service introduced the High Volume Instrument (HVI) measurement as a universal standard index. Trash contents from HVI module represent the trash portion only on a sample’s surface. In additional to HVI’s geometric method, gravimetric-based Shirley Analyzer (SA) and Advanced Fiber Information System (AFIS) also have been utilized to quantify the trash contents. With the increasing acceptance of HVI readings in the domestic and international trading, there is interest in the relationship between HVI and SA trash from cotton customers and regulators. Due to the complexity of not only trash type, size, and weight distribution but also the nature of HVI and SA tests, there have been few studies that compare the two types of trash readings. This study investigated the correlations between two HVI trash readings, and revealed a general conversion of HVIcount=104.5*HVIarea among low trash samples. Then, correlations between the HVI and SA trash and also against AFIS trash were examined, and a stronger relationship between HVI and SA trash than between HVI and AFIS trash was observed. Next, the samples were subgrouped subjectively according to the ratios of HVIarea/SAvisible (or HVIcount/SAvisible), and from the plots with the lowest axis intercept values, it was proposed two general conversions of SAvisible = 6.82*HVIarea and SAvisible = 0.069*HVIcount. To verify the likely conversion, NIR spectra were correlated with HVIarea readings.