Why does a cook time calculator give a window rather than a time?
Because a single number would be a lie. Hours per pound is a planning heuristic, not a
physical law, and the real spread on a long cook is 25 percent or more. Ambient temperature,
wind, humidity, how often the lid opens, the individual animal and whether you wrap all move
it, and thickness moves it more than weight does: a thick twelve pound brisket takes longer
than a flat fourteen pound one, because heat travels inward from the surface.
That is why every schedule on this site plans against the slow end. If a cook finishes
early, a dry cooler packed with towels holds it safely above 140°F for hours and the
problem disappears. If it finishes late, nothing solves it, and dinner is late. Build two
hours of buffer into anything longer than six hours and treat the rest as separate again.
Once the plan exists, the thermometer finishes the job. Every figure these tools produce is
a planning estimate, and doneness is a measurement. Read the
temperature control guide for probe
placement and calibration, and the
stall explainer for why the temperature parks
for hours in the middle of a long cook and why that is normal rather than a fault.