Sorry, I just kind of winged it. Took some measurements, bought some 2x4's and 2x6's and went at it. I put 1/4" MDF on top, over the 2x4's for a smother surface, then added a 1x3 on the edge. The front legs are shorter then the back on purpose, so the 1x3 keeps most of the mess from falling on my lap. Its just a heavy, rigid table. Let me know it you want actual dimensions, but if your chair adjusts up and down, you have some leeway.
Jim