Spatial variations of cortical bone microstructure and mechanics can be described by mapping proton densities as exist in macromolecular, bound, and pore water pools. Comparing bone signal in ultrashort echo time MRI (UTE-MRI) and in inversion recovery UTE MRI against a known external reference signal enabled us to measure total, bound, and pore water proton densities. Measured total water proton density combined with macromolecular fraction from magnetization transfer modelling resulted in macromolecular proton density estimation. We observed strong correlation between proton densities and bone porosity. The developed technique was performed robustly on ten young subjects. This technique may aid diagnosing bone diseases and injuries.