This dataset provides corrected bulk density (BD) values and their associated uncertainty estimates for 4,340 soil genetic horizons across 1,236 monitoring sites of the Hungarian Soil Information and Monitoring System. The correction was achieved by developing a pedotransfer function (PTF) based on the Hungarian Detailed Soil Hydro-physical Database (Hungarian acronym: MARTHA) and advanced machine learning algorithms. Soil properties (i.e., soil organic carbon, pH in water, and sand, silt, and clay content) together with environmental covariates, used as proxies for the soil forming factors, were integrated into the PTF development to improve predictive performance. Uncertainty of the BD predictions is provided in two forms: (1) the 90% prediction interval (defined by its lower and upper limits, within which the true value is expected to occur nine times out of ten), and (2) the standard error of the corrected BD values. To ensure transparency, reproducibility, and open access, the corrected BD values, their corresponding uncertainty estimates, and the developed code are publicly available. For more details / to cite this dataset please use: Sohrab, S., Szabó, B., Pásztor, L., Makó, A., Szatmári, G. (2025). Adjusting bulk density observations in the Hungarian Soil Information and Monitoring System using pedotransfer functions. European Journal of Soil Science 76, e70245. Codes are available on GitHub: https://github.com/Mehrsoh/Soil-BD-Correction Description of the files: Two versions of the same dataset are provided, differing only in file format: (1) "HUN-SIMS_BD_corrected.csv" – CSV format (separated by semicolon), and (2) "HUN-SIMS_BD_corrected.xlsx" – Microsoft Excel format. The table below summarizes the column names, units, and data formats, and also provides a description for each column. Note that the coordinate reference system is the Hungarian Unified National Projection System (HD72/EOV; EPSG: 23700). For more details, see https://epsg.io/23700. Column name Format Unit Description PROFILE_ID string - Identifier of monitoring sites in the Hungarian Soil Information and Monitoring System LAYER_ID string - Identifier of soil genetic horizons at a monitoring site X numeric [m] X coordinate Y numeric [m] Y coordinate TOP numeric [cm] Upper depth boundary of soil genetic horizons BOTTOM numeric [cm] Lower depth boundary of soil genetic horizons BD_CORRECTED numeric [g·cm-3] Bias-corrected bulk density value Q_05 numeric [g·cm-3] 5th quantile; lower limit of the 90% prediction interval Q_95 numeric [g·cm-3] 95th quantile; upper limit of the 90% prediction interval SE numeric [g·cm-3] Standard error of the bias-corrected bulk density value