We have used the Sydney University Stellar Interferometer ( SUSI ) to measure the angular diameter of the F9 V star \beta Virginis .
After correcting for limb darkening and combining with the revised Hipparcos parallax , we derive a radius of 1.703 \pm 0.022 R _ { \sun } ( 1.3 per cent ) .
We have also calculated the bolometric flux from published measurements which , combined with the angular diameter , implies an effective temperature of 6059 \pm 49 K ( 0.8 per cent ) .
We also derived the luminosity of \beta Vir to be L = 3.51 \pm 0.08 L _ { \sun } ( 2.1 per cent ) .
Solar-like oscillations were measured in this star by Carrier et al .
( 11 ) and using their value for the large frequency separation yields the mean stellar density with an uncertainty of about 2 per cent .
Our constraints on the fundamental parameters of \beta Vir will be important to test theoretical models of this star and its oscillations .