How Long to Bake a Potato

The short answer: size and heat set the clock

Baked potato timing comes down to two dials: how big the potato is and how hot the oven is. Everything else, foil, oil, wrapping, rack position, moves the result by a few minutes. The working rate for a russet at 400 F is about 4.6 minutes per ounce, so timing any potato is one multiplication away:

• Small, 8 oz: 8 x 4.6 = 36.8 minutes, call it 30 to 40
• Medium, 12 oz: 12 x 4.6 = 55.2 minutes, call it 50 to 60
• Large, 16 oz: 16 x 4.6 = 73.6 minutes, call it 70 to 80

Those windows assume a preheated 400 F oven and the potato pierced with a fork, sitting directly on the middle rack. If your oven runs cool or you are baking a full tray of potatoes at once, aim for the top of each window.

Worked example: a medium 12 ounce russet at 400 F

Here is the standard weeknight case: one 12 ounce russet, scrubbed, dried, pierced, rubbed with a little oil and salt, and baked directly on the middle rack at 400 F.

• Base time: 12 x 4.6 = 55.2 minutes
• Start checking: 55.2 - 5 = 50.2, so poke it at 50 minutes
• Expected finish: 55.2 + 5 = 60.2, so plan for 60 minutes

At 50 minutes, grab the potato with a folded towel and squeeze. If it yields and a fork slides in without pushing, it is done. If the center resists, give it 10 more minutes and test again. Large russets and dense yellow potatoes are the ones most often pulled early, so for anything above 14 ounces trust the squeeze over the clock.

One line from the USDA's own guidance is worth keeping in mind: potatoes are done by texture, not by a safety temperature, because they grow in soil rather than carrying raw-meat pathogens. The internal starch gelatinizes around 205 to 210 F, which is what the fork test detects.

How size changes the time

Size is the biggest lever, and it is not linear: a 16 ounce potato is twice the weight of an 8 ounce one but takes about double the time, because heat has to travel further into the center. The table below uses the same 4.6 minutes per ounce rate at 400 F.

When a bag holds mixed sizes, sort them. Baking a small potato next to a large one means the small one is overdone and shriveled by the time the large one is ready. Two medium potatoes beat one giant one for even service, and they finish 15 to 20 minutes sooner than a 20 ounce baker would.

The figure below shows how the minutes climb with size.

How oven temperature changes the time

Temperature is the second lever, and it trades time for skin quality. Hotter ovens brown the skin faster but give you less margin for error; cooler ovens are forgiving and fit alongside a roast. The factors below scale the base rate:

Check the arithmetic with the medium potato: at 425 F the time is 12 x 4.6 x 0.88 = 48.6 minutes, which matches the 45 to 55 window. Whatever temperature you pick, preheat fully; a potato that starts in a warming oven loses 10 to 15 minutes and bakes unevenly.

Convection adds one more wrinkle. A convection oven's fan moves hot air across the skin, effectively running about 25 degrees hotter than the dial, so cut about 10 minutes off any 400 F time and start checking early. If your machine toggles between modes, pick one mode for the whole bake; switching midway gives the skin a head start the center never catches up with.

Telling when it is done: poke, squeeze, and internal heat

The clock is a plan; the test is the truth. Two checks cover it. First, the squeeze test: with a folded towel or oven mitt on each side, gently squeeze the potato. Fully baked, the middle gives like a stress ball. Any hard core means more time. Second, the fork test: a fork or thin skewer should slide into the center with no resistance and pull out clean.

If you like numbers, an instant-read thermometer reading 205 to 210 F in the center confirms it. Below that, the starch has not fully gelatinized and the flesh tastes dense and slightly wet. Above about 215 F the skin starts to leathery and the flesh dries. This is also the point where convection ovens mislead: they run effectively 25 degrees hotter, so convert your setting or the skin browns while the center lags.

Skin on or off, foil or dry, oil or not

Skin on is the default for good reason. The skin holds moisture in the flesh, adds texture, and carries most of the fiber. Dry skin crisps in a hot oven; rub it with a teaspoon of oil and a pinch of salt and you get bakery-style results. Peeling before baking is fine for mashed-potato projects, but the exposed flesh dries, so oil it well.

Foil belongs after the oven, not during it. Wrapping a potato in foil and baking steams the skin soft, which is the opposite of the crisp jacket most people want. The bigger issue is safety: the CDC's botulism prevention guidance specifically flags foil-wrapped potatoes left at room temperature, because the sealed, oxygen-poor wrap is where botulism bacteria can grow. Hold baked potatoes warm in a 200 F oven or the fridge, unwrapped, and reheat before serving. Utah State University Extension's baking guidance for potatoes follows the same wash, pierce, and bake-until-tender pattern.

Baking more than one, and make-ahead notes

Batch baking barely changes the math. Four potatoes on the rack take the same time as one, as long as they are the same size and none of them touch; heat circulates around each potato. A fully packed sheet tray slows things by 10 to 15 minutes. For six or more, use two racks with space between, and swap racks halfway through.

Leftovers keep 3 to 4 days refrigerated. To revive the skin, skip the microwave and use a 350 F oven for 15 to 20 minutes, or a hot skillet for split potatoes. If dinner runs late, the 200 F hold is your friend: a finished potato waits an hour without quality loss, and beyond that the flesh starts drying at the open ends.

One last habit worth picking up: start the potatoes before the main dish, not after. Potatoes forgive an early finish better than almost any side, because a done potato holds happily in a 200 F oven for up to an hour, while a roast or casserole that runs late rarely does the reverse. Build the schedule around the longest item and let the potatoes wait their turn.