These data were produced within the objectives of the NERC grant (alongside collaborator Gibbs at NOC, Southampton) and predominantly comprise biometric data collected under light microscope at x1500 magnification from the coccolithophore taxon Coccolithus pelagicus, a heavily calcified taxon with a long fossil record. The data was collected as part of a collaborative research effort bringing together the modern and fossil consortia within the UK Ocean Acidification research programme. The data are from batch culture experiments on both modern sub-species of C. pelagicus and provide cell size, coccosphere size, coccolith size and number of coccoliths per cell. The same parameters were measured from C. pelagicus from North Atlantic field and sediment trap samples from inside and outside bloom conditions. Again, the same parameters were also measured from C. pelagicus from exceptionally well-preserved fossil material from several shelf and off-shelf marine locations including New Jersey, Tanzania, California and the Bay of Biscay.