Internal Temperature

Internal temperature is the temperature at the coldest point inside a steak, which is the geometric center of the thickest section. This is the definitive, objective measurement of doneness — more accurate than time, touch, color, or any other indicator.

Why the geometric center: It's the last point to reach the target temperature. If the center is 131°F, you know the entire steak is at or above 131°F (since the outer layers are always warmer). Measuring off-center gives a falsely high reading — you might think the steak is done when the actual coldest point is still 10°F below target.

How to measure accurately: Insert the thermometer probe from the side of the steak, pushing it to the geometric center. For uniform-thickness steaks, this is straightforward. For tapered cuts (like a tri-tip), measure the thickest section. For bone-in cuts, insert from the side away from the bone — bone conducts heat differently and the adjacent meat will be warmer than the center of the muscle.

Instant-read vs. leave-in probes: Instant-read thermometers (like the ThermoWorks Thermapen) give a snapshot. Leave-in probes (like the ThermoWorks Smoke) provide continuous monitoring throughout the cook — letting you track the rate of temperature change and predict when to pull.

Key temperatures to know: - 131°F: Center of the medium-rare sweet spot - 140°F: Actin denaturation begins — moisture losses increase significantly - 145°F: USDA recommended minimum for whole-muscle beef - 160°F: USDA recommended minimum for ground beef