I've been doing some math on the radius of the core (inner core in particular), and I keep getting what look like nonsense results. The composition is supposedly nearly all iron, close enough to it anyway... and I've been using (avg) densities as high as 13,000kg/m3. However, even with density this high I can't get a lower radius than about 2500km. This is using a 0.16 mass for the inner core.
Google returns a radius of 1220km for the inner core. It also returns a diameter of 1220km for the inner core.
I went so far as to reimplement this an an Excel spreadsheet to double check my code, and I get consistent results.
Is there a good source for the (rough is fine) densities, mass, and radii of the geological layers? I don't trust Google and Wikipedia at this point, and even if I find the answer somewhere else I won't know for sure if they're even close to correct.