  The proton is a fundamental constituent of matter. It is an extended object
with finite size that can be inferred with some degree of accuracy from several
measurements. Using constraints from the analytic behavior of the form factors
we present here a model-independent study that extracts the proton magnetic
radius from scattering data. From electron-proton scattering data we find
$r_M^p = 0.91_{-0.06}^{+0.03} \pm 0.02$ fm. When we include electron-neutron
scattering data and $\pi\pi$ data, we find $r_M^p = 0.87_{-0.05}^{+0.04}\pm
0.01$ fm and $r_M^p =0.87_{-0.02}^{+0.02}$ fm respectively. The neutron
magnetic radius is extracted as $r_M^n = 0.89_{-0.03}^{+0.03}$ fm combining all
three data sets.
