A new lightweight portable manometer-sedimentation (m-Sed) system has been developed for determining particle size distributions (PSDs). The m-Sed test is appropriate for the full sand size range spanning from 0.075 to 4.75 mm. In contrast to an earlier electronic system using a pressure transducer, the m-Sed test employs a simple polyurethane rubber manometer tube with a 3.2-mm inner diameter connected to a 25.4-mm-diameter sedimentation column. This eliminates all reliance on electricity and facilitates testing at remote field locations. This article presents the test hardware, derives m-Sed’s fundamental governing equations, and compares the PSDs by m-Sed with results by sieving. Tests conducted on eight engineered sand specimens demonstrated excellent agreement between PSD curves produced by the m-Sed and sieve methods. Additional investigations confirmed m-Sed test repeatability and showed complete agreement with results using a pressure transducer. A parametric analysis using the Corey shape factor showed that the influence of particle shape on settling velocities is most pronounced for coarse particles, diminishes for medium sizes, and becomes negligible for fine sand. The m-Sed test also provides very accurate measures of specific gravity and specimen mass. Practical considerations regarding the selection of optimal manometer tube diameter and material are discussed. The m-Sed test’s operational simplicity, portability, reliability, and accuracy position it as a proven alternative to sieving for PSD analysis of sands.