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In Australia, arid and semi-arid rangelands cover vast areas, and contribute to the livestock industry, carbon market, and provision of other ecosystem services. Because of their extent, even minor changes in rangeland soil organic carbon (SOC) stocks on a per-area basis may significantly impact the terrestrial carbon budget. Estimation of SOC stocks from soil C concentrations requires estimates of gravel content, sampling thickness and soil bulk density (BD). However, BD is a major source of uncertainty, a nd determination of SOC stocks is often limited by challenges in BD estimation. In the absence of measured BD values, alternatives such as digitally mapped spatial layers are used to derive BD but these values are at relatively low resolution, are static and have relatively high uncertainty. Due to inherently low SOC stocks in rangeland ecosystems, accurate estimation of BD is important to detect temporal change. The most effective method for measuring BD will depend on factors such as soil type and moisture conditions at sampling. Here we compared estimates of BD to 50 cm sampling depth across several rangeland sites derived from different field methods including: i) the mass of whole soil and volume of carbon concentration cores, corrected for oven-dry moisture content; ii) the mass of whole soil and volume of brass rings collected from soil pit s corrected for oven-dry moisture content; and iii) in situ gamma-neutron gauge measurements of dry density adjacent to a subset of the cores. Under relatively dry soil conditions, the soil core method gave inconsistent and sometimes spurious results. By comparison, the other methods gave more consistent results. These differences have significant implications for the subsequent estimation of SO C stocks. Our results inform optimal pathways for estimating BD in arid and semi-arid rangelands to allow more accurate calculation of stocks and change detection over time.