To bake a sweet potato at 400°F, the typical baking time depends on the size and whether it is whole or cut:

• For a medium whole sweet potato (about 3-4 inches wide), bake for approximately 35 to 50 minutes until tender and easily pierced with a fork

• Larger sweet potatoes (5 inches or more) may take around 50 to 60 minutes at 400°F

• If the sweet potato is cut in half lengthwise, bake cut side down for about 40 minutes until juices bubble and the flesh is soft

• To check doneness, the potato should be soft enough that a fork slides in easily, the skin may become wrinkly, and the internal temperature should reach about 205-210°F

• For best results, prick the sweet potato with a fork before baking to allow steam to escape and prevent bursting

In summary, baking a medium whole sweet potato at 400°F usually takes about 40-50 minutes, while larger ones may require up to an hour. Cut sweet potatoes bake a bit faster, around 40 minutes. Always test for softness to ensure they are fully cooked.