We developed an improved Hg-displacement method to measure the density of 1-to 2-mm-diameter soil aggregates. The proposed method reduces the intrusion of Hg into the intra-aggregate pore volume of the soil aggregates, common in previous methods. Aggregate density is defined as the weight (g) of dry soil aggregates divided by the volume (cm3) of soil aggregates and would include all intra-aggregate pores and exclude all interaggregate pores. Our measured density of soil aggregates was calculated by dividing the oven-dried mass by the volume of displaced Hg at a low pressure. Particle density of soil aggregates was measured using a helium pycnometer. The proposed method of measuring the density of soil aggregates by evacuation followed by Hg displacement at low pressure will lower the density value estimates compared with those measured by previous Hg displacement methods using a pressure higher than atmospheric pressure.