Research was conducted to investigate ways of reducing trash measurement differences between High Volume Instruments (HVIs) and the master instrument used for establishing trash measurement standards. To meet these objectives, several tile sets were constructed with circular and square particles of varying sizes to study the effects of particle size, particle shape and various contrasting backgrounds. HVI and master instrument measurements of total particle area and total particle count were made on these tile sets and on actual cotton calibration sets. Particle areas were also calculated from visual measurements made with a precision ruler and magnifying glasses. Results showed that particle areas measured with the master instrument agreed closely with areas calculated from visual measurements. HVI area measurements were inflated at an increasing rate as average particle size decreased. Corrections based on circular and square particles were developed and applied to HVI total area measurements. These corrections effectively eliminated the particle size inflation effect when all particles were equal in size and shape. Effectiveness of the corrections was reduced as measured particles became less uniform in size. Relative to standard test methods, the developed corrections were effective in improving HVI and master instrument trash measurement agreement on cotton trash calibration sets. Particle to background contrast results showed higher total particle area measurements as contrast increased on both the HVI and the master instrument.