Recent xschem sky130 symbols show the approximated capacitance as calculated from W, L, MF:

C=MF * (W * L * 2e-15 + ( W + L ) * 0.38e-15)

the two parameters are the area capacitance (camimc) and perimeter capacitance (2 * cpmimc) in the typical corner. The shown values are of course only an approximated value.