<p>Carotid atherosclerotic plaques have a three-dimensional shape on initial detection and progress in their contour and size in all three directions over time. To estimate the plaque volume, we measured circumferential (<i>c</i>_<i>p</i>) and sagittal (<i>l</i>_<i>p</i>) length, and mean of luminally protruding thickness (<i>t</i>_<i>mean</i>) from axial and sagittal carotid duplex ultrasonography (CDU) images of the carotid plaques. Then, we calculated plaque volume using the hemi-ellipsoid volume formula (<i>π</i>[<i>c</i>_<i>p</i> × <i>l</i>_<i>p</i> × <i>t</i>_<i>mean</i>]/6) with the three axis values. We logically validated that the hemi-ellipsoid volume formula could be applied to estimate the volume of all plaques with smooth or irregular thicknesses and involving the partial or entire axial lumen. The hemi-ellipsoid volume evaluations were a better tool to assess severity and atherosclerotic burden of carotid atherosclerotic plaques on follow-up than one-dimensional diameter ([1-{stenosis/lumen diameter}] × 100%) and two-dimensional area stenosis ([1-{stenosis/lumen area}] × 100%) evaluations. The present study showed successful implementation of the hemi-ellipsoid volume formula to logically measure plaque volume. The logical volume estimation was better for evaluating and monitoring the severity and atherosclerotic burden of carotid plaques.</p>