diff --git a/NuclearRMF.jl b/NuclearRMF.jl
index 9877aad..ffd91b5 100644
--- a/NuclearRMF.jl
+++ b/NuclearRMF.jl
@@ -45,3 +45,9 @@ function solve_system!(s::system; reinitialize_densities=true, monitor_print=tru
         previous_E_per_A = E_per_A
     end
 end
+
+"Calculate RMS radius from density"
+rms_radius(p::Bool, s::system) = 4pi * Δr(s) * sum((rs(s) .^ 4) .* (p ? s.ρ_vp : s.ρ_vn)) / (p ? s.Z : s.N) |> sqrt
+
+"Calculate neutron skin thickness"
+R_skin(s::system) = rms_radius(false, s) - rms_radius(true, s)