  We present the observational mass-radius (M-R) relation for a sample of 47
magnetized white dwarfs (WDs) with the magnetic field strength (B) ranging from
1 to 773 MG, identified from the SDSS data release 7 (DR7). We derive their
effective temperature, surface gravity (log g), luminosity, radius, and mass.
While atmospheric parameters are derived using a Virtual Observatory Spectral
Energy Distribution Analyzer (VOSA), the mass is derived using their location
in the HR diagram in comparison with the evolutionary tracks of different
masses. We implement this mass measurement instead of a more traditional method
of deriving masses from log g, which is unreliable as is based on SED and
generates errors from other physical parameters involved. The main disadvantage
of this method is that we need to assume a core composition of WDs. As it is
complicated to identify the exact composition of these WDs from low-resolution
spectra, we use tracks for the masses 0.2 to 0.4 solar mass assuming a He-core,
0.5 to 1.0 solar mass assuming CO core, and above solar mass assuming O-Ne-Mg
core. We compare the observed M-R relation with those predicted by the finite
temperature model by considering different B, which are well in agreement
considering their relatively low surface fields, less than or of the order of
10^9 G. Currently, there is no direct observational detection of magnetized WDs
with B > 10^9 G. We propose that our model can be further extrapolated to
higher B, which may indicate the existence of super-Chandrasekhar mass (M > 1.4
solar mass) WDs at higher B.
