  We show how gravitational-wave observations with advanced detectors of tens
to several tens of neutron-star binaries can measure the neutron-star radius
with an accuracy of several to a few percent, for mass and spatial
distributions that are realistic, and with none of the sources located within
100 Mpc. We achieve such an accuracy by combining measurements of the total
mass from the inspiral phase with those of the compactness from the postmerger
oscillation frequencies. For estimating the measurement errors of these
frequencies we utilize analytical fits to postmerger numerical-relativity
waveforms in the time domain, obtained here for the first time, for four
nuclear-physics equations of state and a couple of values for the mass. We
further exploit quasi-universal relations to derive errors in compactness from
those frequencies. Measuring the average radius to well within 10% is possible
for a sample of 100 binaries distributed uniformly in volume between 100 and
300 Mpc, so long as the equation of state is not too soft or the binaries are
not too heavy.
