This dataset presents estimates of mean values within selected habitats and parent material characteristics made using Countryside Survey (CS) data from 1978, 1998 and 2007 using a mixed model approach (see Scott, 2008 for further details of similar statistical analysis - http://nora.nerc.ac.uk/id/eprint/5202/1/CS_UK_2007_TR4%5B1%5D.pdf ). Countryside Survey topsoil carbon data is representative of 0-15 cm soil depth and includes Loss-on-ignition (%), Carbon concentration (g kg-1) and Carbon density (t ha-1). A total of 2614 cores from 591 1km x 1km squares across Great Britain were collected and analysed in 2007 (see Emmett et al. 2010 for further details of sampling and methods http://nora.nerc.ac.uk/id/eprint/5201/1/CS_UK_2007_TR3%5B1%5D.pdf ). Loss-on-ignition (LOI) was determined by combustion of 10g dry soil at 375 deg C for 16 hours; carbon concentration was estimated by multiplying LOI by a factor of 0.55, and carbon density was estimated by combining carbon concentration with bulk density estimates. The estimated means of habitat/parent material combinations using 2007 data are modelled on dominant habitat and parent material characteristics derived from the Land Cover Map 2007 and Parent Material Model 2009, respectively. The parent material characteristic used was that which minimised AIC in each model (see Supporting Information). Areas, such as urban and littoral rock, are not sampled by CS and therefore have no associated data. Also, in some circumstances sample sizes for particular habitat/parent material combinations were insufficient to estimate mean values. The Countryside Survey looks at a range of physical, chemical and biological properties of the topsoil from a representative sample of habitats across the UK. Full details about this dataset can be found at https://doi.org/10.5285/9e4451f8-23d3-40dc-9302-73e30ad3dd76