This dataset presents the mean topsoil (0-15 cm) organic carbon concentration (g kg-1) and measures of its variability at 1 km resolution across Great Britain. The mean and variability metrics were calculated from an ensemble of eight previously published digital soil maps applied to all 1 km grid cells across GB where data were available from all eight maps. Four of the maps were generated from the 2007 UKCEH Countryside Survey topsoil data, two of which are available online to use. Two maps are from the International Soil Reference and Information Centre, ISRIC: SoilGrids250m v.1 (2017) and v.2 (2020) which are free to download. Two maps are from the EU’s Joint Research Centre (JRC): the OCTOP map of 2004 and LUCAS map of 2014 which are both free to download. The dataset comes in the form of a seven-band raster tiff file, with each band representing the following: 1. Mean predicted soil organic carbon concentration (g kg-1) of all eight maps at each 1 km grid cell 2. Standard deviation (g kg-1) of all eight maps at each 1 km grid cell 3. Coefficient of variation (unitless; the standard deviation divided by the mean) at each 1 km grid cell 4. Signal to noise ratio (unitless; the mean divided by the standard deviation) at each 1 km grid cell 5. Name of the map that deviates the most from the ensemble mean at each 1 km grid cell 6. Relative size (%) of the largest difference from the ensemble mean at each 1 km grid cell 7. Relative size of the largest difference from the ensemble mean expressed as the number of standard deviations exceeded at each 1 km grid cell This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability. Full details about this dataset can be found at https://doi.org/10.5285/c3b400ea-f603-4bc2-9225-5f1abfa9fe65