In this work, we analyze how the variation of cell size influences the volume calculated from LiDAR-derived DEMs in two coastal Late Holocene dune fields located in southern Brazil. Cell size varied from 1 to 100m. The RMSE of the resampled DEMs about the original LiDAR (with 0.5m resolution) increases linearly with cell size, while the R-squared decreases following a second-order trend. The volume does not show a simple linear or exponential behavior, but fluctuates, with positive and negative deviations from the original DEM. This can be explained by a randomness on the position of the cell about the landforms and a relationship between cell size and landfom size. Volumes from SRTM deviated less than 10% about the reference data and are considered suitable as input for numerical simulations of Quaternary coastal evolution models, as these values should be within the expected range for time spans of hundreds to thousands of years.