Using 1 x 12 stock, the sides would be 11 1/4 inches, plus 3/4 inch added apiece by the front and back boards, for a total of 12 3/4 inches. I figured out the width by looking at a video of Schwartz hoisting the chest. We're about the same size, so comparing his arm span to mine, I figured it to be about 30 inches.

In this class, you can choose between making a full-size chest (25-3/4” tall, 24” front to back, 40-1/4” long) or a traveling version that will fit into the back of a car or truck (14-1/2” high, 19-1/2” front to back, 39-1/2” long).