How long to smoke an 18 lb turkey at 300°F

Work backwards from the long end. To serve an 18 lb turkey at 6pm on a Saturday, light the smoker around Saturday 7:21am — 10h 39m earlier.

That asymmetry is deliberate. Finished barbecue sits in a cooler for hours and arguably improves; an unfinished one at dinner time is not a problem you can solve. Being early is recoverable, being late is not.

The smoker calculator turns your own serve time into a clock time, and handles weights and temperatures between the ones charted here.

At 10h 39m you are not staying awake for this. There are two workable plans and one bad one.

Start the evening before and sleep through the long middle stretch — a pellet grill holds its own temperature, which is what makes this the common choice. Or start at dawn and hold it: finish in the afternoon, wrap it, and rest it in a dry cooler until dinner. A well-packed cooler holds serving temperature for hours, and the rest does the meat good.

The bad plan is starting in the morning and hoping. That is the version where dinner is at 11pm.

Sleeping through it assumes something is watching. An instant-read probe only answers when you open the lid, so for the overnight stretch the tool is a leave-in one: the ThermoWorks Signals runs three meat probes and an air probe at once and sends the readings to your phone over Wi-Fi, so both the turkey and the smoker around it are on the screen by the bed.

The same turkey can finish hours apart between cooks. Grade, fat, airflow, ambient temperature and how often the lid comes off all move the number, and a calculator can see none of them.

So the figures above are a window, not a prediction. A page that told you “9h 54m exactly” would feel more precise and be less true.

USDA FSIS — Turkey: Alternate Routes to the Table publishes one rate for the whole 225–300°F smoker band: “Estimate 20 to 30 minutes per pound if using a smoker.” Our figure at 300°F runs to 33 minutes a pound, past USDA's 30. That extra is ours, not USDA's: we split the rate by temperature and plan each figure from the long side, because a bird that finishes early can rest and one that finishes late cannot be hurried. Read it.

Pull between 165–175°F internal. The USDA safe minimum for this cut is 165°F, which is a food-safety floor rather than a target.

Below 275°F the skin does not render properly. Breast to 165°F, thigh to 175°F.

That window is an internal temperature, and it is not what the lid gauge shows — a dome thermometer reads the air under the lid, not the centre of the meat. Hitting a 10°F window means measuring the meat itself, which is what an instant-read probe is for.

Safe minimums from the USDA FSIS Safe Minimum Internal Temperature Chart.

On a pellet grill at 300°F, this cook burns roughly 10.8–21 lb of pellets — so have two 20 lb bags on hand. Cold and windy days push that higher.

For an offset or a charcoal cooker there is no figure here, and that is on purpose. Consumption depends on firebox size, wood species, split moisture and how the pit is run, and a number would be a guess wearing an estimate’s clothes.

At the long end that is more than the smallest hopper on the grills we compare, which publish 13.5 lb upwards — so this cook can outrun a single load. The pellet grill comparison has the capacities.