If your temperature is set to between 225-250°F expect about 1-1 ½ hours of cook time per pound. This is certainly not a rule to follow too closely, as there are multiple factors to consider.
How big is your brisket?
A whole brisket can weigh anywhere between 10-16 pounds, and it can take a long time for the heat to reach the center of a piece of meat this size. If you keep the brisket at room temperature for an hour or so before cooking, the beef is allowed to temper, and the heat will penetrates the meat at a more consistent rate.
What kind of smoker are you using?
Electric and gas smokers are fantastic for regulating consistent temperatures, but if you are smoking using more traditional means like a barrel or pit smoker you will have more of a cooking temperature variance. This is due to the fact that initially, a fire is created, and that fire eventually creates the hot embers that will slowly cook your brisket. This heat gradually reduces during the cooking process. Different smokers operate differently, so it is never accurate to adhere to a specific time when cooking a piece of meat this large.
How often are you opening the smoker?
Keep the smoker closed as much as possible and only open it if you really have to. Opening a smoker releases both precious heat and smoke flavor.
Are you letting your brisket rest?
Brisket should rest for several hours before slicing or chilling to help maintain juices and assure a tender product. I like to remove the brisket from the smoker, wrap it in plastic, next wrap in a clean towel, and pack into a cooler for a while.
My best advice for smoking brisket is to never allow the cooking temperature to exceed 280°F and invest in a good thermometer so you know where you are at any given point. Want to learn more about smoking brisket? We’ve written a guide to the best wood for smoking brisket and how to smoke a brisket in a barrel smoker.