This was, I think, half of a 5 foot by 3 foot (Peter Pig size board) so was 36 inches by 30 inches. This was a bigger than I had wanted. It certainly wouldn't fit on my lap whilst ensconced in the comfy chair. However it was fine on the coffee table.
I have drawn on 4 inch squares with a central dot in each square to accommodate the Napoleonic stuff I have based on 2" squares. It will certainly be big enough for a corps v corps battle if one base equates to a regiment or brigade.
The shed also gave up a smaller board of 24 inches by 30 inches. Just bare mdf so I will give it a lick of paint or two at the weekend; green one side and desert the other.
I have some where a box of seven years war 6mm stuff, I haven't used for years, which I think I will base up on 4cm squares. The smaller board will give a 15 by 20 grid of 4cm squares plenty for a decent little "laptop" game.
I may also have some colonial stuff too. Oh dear megalomania strikes again.