This varies, and depends on different factors: #1 BTU Output: the higher the BTU the more propane it uses. #2 Usage: How often you use it and for how many hours. #3 Setting: The higher the setting the more propane your fire pit will use. If run on the highest setting a 20-pound tank will run for approx. 7.5 hours to 11 hours. Tip:  Above all, keep a backup at the ready.  It’s not very nice when you run out of gas and the fun is just beginning. (Voice of experience talking here.)