A method and apparatus for evaluating the size and/or quality of a spot weld. The apparatus includes a two-dimensional array of ultrasonic transducers arranged with a delay line for positioning adjacent a surface of a weld. A layer of gel is placed between the delay line and the weld surface. The array of transducers emit ultrasonic waves that pass into the weld. The reflected waves are received by the transducers and relayed to a central processing unit that analyzes the time delay, amplitude, and amplitude attenuation to calculate the border of the weld nugget, the thickness of the welded material, the thickness of the gel layer, and other factors contributing to weld quality.