It's an odd shape to measure, as it's approximately 15 inches long, with a 12 inch diameter bowl. The extra, is the handles, on the base frame for the bowl. It's around 13 inches tall handle down, 16 inches when it's up and which increases by 3 inch increments, when you add the rings.
I've seen pizza and chips done in one, on the coffee table, with no damage to the table!
I bought a nice sheet of PINE, [ which cost almost as much as the oven,, ] from B&Q, cit it to fit on the top of the hob, and it works great, you have to place it first, then take away after use, but, what the hell, no problem, wifes happy, and the halogen oven is a cracker, BEST on the market,