I tried an experiment this afternoon when I cut the grass. Normally, I fill up the mower with gas before I cut the yard, but I wanted to see just how far I could go without filling up. (Also, I was feeling lazy and did not want to go back out to the gas station this evening.) I knew that I had already done the front and back yards once on the gas that was already in the tank, so without filling up, I proceeded to cut the grass.
I was able to mow all of the front and side yards, and a few strips of the backyard (perhaps 1/5) before I ran out of gas. That means I can do about 1.6 yards worth of mowing on a tank. It’s an old and inefficient mower, but it cost me $50 when I got it and it hasn’t given me trouble so what the heck.