Baked sweet potato

How long to bake a sweet potato at 400°F

At 400°F, a medium sweet potato of 7 to 9 oz takes 45 to 60 minutes. Size matters more than anything else, so pick potatoes of about the same size and thickness if you want them done together. As a guide, at 400°F:

• Small, 5 to 6 oz: 40 to 45 minutes
• Medium, 7 to 9 oz: 45 to 60 minutes
• Large, 12 oz or more: 60 to 75 minutes

At 425°F, take off about 10 minutes. At 350°F, add 15 to 20 minutes. 350°F is useful when the oven is already on for something else, like a roast or a casserole, and the result is just as good.

How to tell when a baked sweet potato is done

A knife or skewer should slide into the thickest part with no resistance at all, and the potato should give when you squeeze it with an oven mitt. Often the skin puffs away from the flesh and dark syrup bubbles out onto the pan. If you have an instant-read thermometer, aim for 205 to 210°F in the center. Firm in the middle means it needs longer. An underbaked sweet potato is starchy and dry, and it is very hard to overbake one in its skin.

Why baked sweet potatoes taste sweeter

Sweet potatoes contain an enzyme that turns some of their starch into sugar as they heat. It stops working once the inside gets much past 170°F. A slow bake keeps the potato in that range for a long time, so an oven-baked sweet potato comes out sweeter and more syrupy than a microwaved one, which passes through the range in minutes. That is the main reason to bake them, and the reason not to rush them with a very hot oven.

Foil or no foil

Do not wrap them. Foil traps the steam, so the potato steams in its own moisture and the skin turns soft and wet. Bake them bare, straight on a sheet pan lined with foil or parchment. The lining is there to catch the syrup that leaks out, which otherwise burns onto the pan. Pricking the skin a few times with a fork lets steam out. A sweet potato rarely bursts, but it costs nothing to prevent it.

Sweet potatoes in the air fryer

Whole sweet potatoes come out very well in the air fryer, with a crisper skin than in the oven. Scrub, dry and prick them, rub with a little oil and salt, and air fry at 380°F:

• Medium, 7 to 9 oz: 35 to 45 minutes, turned halfway
• Large, 12 oz or more: 45 to 55 minutes

Leave space around each one for the air to move, which in most baskets means two or three at a time. For cubes, cut them 3/4 inch, toss with 2 tsp oil per pound, and air fry at 400°F for 15 to 18 minutes, shaking the basket twice.

Roasted sweet potato cubes in the oven

For a side that is done in half the time, peel or just scrub the potatoes and cut them into 1-inch cubes. Toss with 1 tbsp olive oil per pound, salt and pepper, and spread them in one layer on a sheet pan. Roast at 425°F for 25 to 30 minutes, turning once, until browned at the edges. Do not crowd the pan, or they steam and stay pale. Smoked paprika or cumin with the salt is good, and they roast in the same time as butternut squash cubes, so the two can share a pan.

In the microwave

For one potato in a hurry, prick it, set it on a plate and microwave on high for 5 to 8 minutes, turning it over halfway, until soft. It will be less sweet and the skin will be soft. To get some of the texture back, finish it in a 425°F oven or the air fryer for 10 minutes.

Sweet potato or yam

In most US grocery stores, the orange-fleshed tubers labeled "yams" are sweet potatoes. True yams are a different plant, with rough, bark-like skin and white, starchy flesh, and are mostly sold in Latin American, African and Asian markets. Any orange sweet potato works here, whatever the sign says. Garnet and Jewel are the most common varieties. White and purple sweet potatoes are drier and take a few minutes longer.

Toppings, with the numbers

• Greek yogurt and chives: 2 tbsp of plain nonfat Greek yogurt adds about 20 kcal and 3 g of protein, and replaces sour cream.
• Chili: a ladle of vegetarian chili makes a stuffed sweet potato a full dinner, with about 16 g of protein in a full bowl.
• Black beans, salsa and avocado: 1/2 cup black beans adds about 110 kcal and 7 g of protein.
• Crunchy chickpeas: a spoonful of oven-roasted chickpeas, made as in our guide to how to cook chickpeas, with tahini and lemon.
• Sweet: cinnamon and 1 tsp maple syrup, about 17 kcal. For the full holiday version with eggs, pecans and a topping, see our sweet potato casserole.

Make ahead

Baked sweet potatoes keep 4 to 5 days in the fridge, whole and in their skins. Reheat them in a 375°F oven for 15 to 20 minutes or in the microwave for 2 to 3. Cold baked sweet potato is good too, cubed into a salad or packed for lunch next to leftover chicken or fish. Scooped out and mashed, the flesh freezes for 3 months.

What it is worth nutritionally

A medium sweet potato baked with a teaspoon of butter has about 215 kcal, with 3 g of protein, 5 g of fat and 40 g of carbohydrate, including about 6 g of fiber. Without the butter it is about 180 kcal. Much of the fiber is in and just under the skin, so eat it if you can. Orange sweet potatoes are one of the richest sources of beta-carotene there is, and one medium potato gives well over a full day's vitamin A. They are also a good source of potassium and vitamin C. Baked sweet potatoes raise blood sugar faster than boiled ones, for the same reason they taste sweeter: more of the starch has already turned to sugar. Eating them with some protein and fat slows that down. It is gluten-free as written, and vegan with olive oil in place of the butter.