Roentgen to rad conversion factor

Answer 1

1 roentgen=.876rad

This is for Exposure (always in air) to Dose (in rad) in air.

For Dose in other materials, the Roentgen-to-Rad conversion factor (often called f-factor) varies quite a bit.

For example, the f-factor for dose absorption in bone is ~4x higher than the f-factor for absorption of dose in tissue when the energy range is ~ 100 keV.

f-factor = W/e [J/C] *2.58E-4 [C/kg/R]

where

W is Average Energy expended in air per ion pair formed

e is electron charge (1.602E-19 C/ion pair))

and 2.58E-4 [C/kg/R] is a unit conversion from Roentgens to SI units [Coulomb/kilogram].

W varies quite a bit from material to material.