Sizing of cracks in the range of tens of micrometers by laser-generated surface acoustic wave (SAW) pulses with a bandwidth of up to 200 MHz is reported. The radius of a semicircular surface-breaking crack was evaluated using two methods, one based on the experimentally measured reflection coefficient and the other on the frequency dependence of the phase lag of the transmitted wave. These quantities were also simulated numerically by means of the finite differences method and fitted to the experimental ones by varying the assumed size of the crack. In both cases the interaction between crack faces was taken into account by an effective interfacial stiffness parameter and the crack sizes obtained acoustically were compared with those measured by optical microscopy. Nondestructive evaluation was extended to the characterization of real microcracks in the range of tens of micrometers with the laser-based pump-probe technique. The microcracks studied were generated in fused silica by strongly nonlinear SAW pulses with shocks in a separate experiment.