To bake sweet potatoes at 400°F, the typical baking time ranges from about 40 to 60 minutes depending on their size and whether they are whole or halved:

• For whole sweet potatoes, bake for approximately 45 to 60 minutes until they are very tender and a fork easily pierces through the skin and flesh

• Smaller sweet potatoes (under 2 inches wide) may be done in about 30 minutes, medium-sized around 1 hour, and large ones up to 1 hour 15 minutes

• If you slice the sweet potatoes in half lengthwise, they cook faster, generally around 40 minutes, placed cut side down on a baking sheet

• To check doneness, gently squeeze the potato with an oven mitt or pierce with a fork; it should feel soft and tender

• For best results, prick whole sweet potatoes with a fork before baking to allow steam to escape

In summary, baking whole sweet potatoes at 400°F usually takes about 45 to 60 minutes, while halved ones take closer to 40 minutes. Adjust time based on size and check tenderness to ensure they are fully cooked.