This dataset contains gridded workday population estimates with a spatial resolution of 1 km x 1 km for the UK based on Census 2021 (Census 2022 for Scotland) and Land Cover Map 2021 input data. While traditional residential population data reflects where individuals live, these workday estimates account for the movement of the population during typical working hours, redistributing the census population based on employment locations and commuting flows. Data on population distribution for the United Kingdom is available from statistical offices in England, Wales, Northern Ireland and Scotland and provided to the public e.g. via the Office for National Statistics (ONS). Population data is typically provided in tabular form or, based on a range of different geographical units, in file types for geographical information systems (GIS), for instance as ESRI Shapefiles. The geographical units reflect administrative boundaries at different levels of detail, from Devolved Administration to Output Areas (OA), wards or intermediate geographies. While the presentation of data on the level of these geographical units is useful for statistical purposes, accounting for spatial variability for instance of environmental determinants of public health requires a more spatially homogeneous population distribution. For this purpose, the dataset presented here combines 2021/2022 UK Census population data on Output Area level with Land Cover Map 2021 land-use classes 'urban' and 'suburban' to create a consistent and comprehensive gridded workday population product. The mapping product is based on British National Grid (OSGB36 datum). Census data from the Office of National Statistics, National Records for Scotland and Northern Ireland Statistics and Research Agency have been downloaded as CSV/Excel files (as outlined in Collection Methods). To ensure consistency of the final product, total population numbers were compared, at each processing step, with the official 2021/2022 Census totals. As a result, the final output file is consistent with the Census total population for the UK in 2021 Full details about this dataset can be found at https://doi.org/10.5285/e7456cd0-9322-4794-953b-baf7d49231e1