Ionised Mass and Free-Free Emission Budget of the Young Nebula NGC 7027

This paper computes a self-contained budget for NGC 7027 from published observational values, with every derived number produced by the deposited computation script. NGC 7027 is a young, carbon-rich and exceptionally dense planetary nebula whose radio continuum is bright enough to serve as a flux-density calibrator. Because it is compact and dense, its ionised mass is sensitive to the distinction between the local electron density measured from line ratios and the root-mean-square density implied by the emission measure. The ratio of those two densities gives the volume filling factor directly, and the filling factor in turn controls whether the ionised mass is a few hundredths or a few tenths of a solar mass. The headline results are: R_pc = 0.045; local_density_cm3 = 6e+04; filling_factor = 0.3; rms_density_cm3 = 3.29e+04; ionised_mass_Msun = 0.199; recombination_time_yr = 2.11; emission_measure_pc_cm6 = 9.72e+07; electron_temperature_K = 1.05e+04. The filling factor is well below unity, so the nebula is clumped rather than uniformly filled. Even with that correction the ionised mass remains modest, which means most of the ejected envelope in this young object is still neutral or molecular rather than ionised. The free-free budget is consistent with the observed radio brightness only when the clumping is included; a uniform-density model overpredicts the mass at fixed emission measure. The calculation is presented with its inputs, relations and sensitivities stated openly, so that any revised distance, density or stellar parameter can be substituted and the verdict recomputed directly.