Standing wave ratio, reflection coefficient, return loss and mismatch loss are all the same fact in different clothes. These conversions are exact — there is no approximation here to improve on.
One mismatch fact, in four different clothes.
SWR, reflection coefficient, return loss and mismatch loss all describe the same thing: how much power bounces back off an imperfect match.
SWR is measured at one point on one frequency — feedline loss actually makes the SWR at the shack look better than it is at the antenna.
