The dataset consists of three spreadsheets that contain all the data used to generate Figures 2, 3 and 4 of the paper, "Optimisation of the cladding structure to minimise surface roughness scattering in antiresonant, hollow-core fibres". All the results were generated with the finite element simulation code COMSOL Multiphysics 6.3. The data consists of the real and imaginary parts of the effective index, together with computed values of the normalised electric field intensity, F, for each boundary and component in the relevant fibre structure, as described in the paper. The raw values of F are scaled by dividing by (wavelength^2)/(core_radius^3) (as described in the paper), and so all the data values are dimensionless.