To bake a whole sweet potato at 400°F (204°C), it generally takes about 45 to 60 minutes depending on the size of the potato. Smaller sweet potatoes may take around 30 to 40 minutes, medium ones about 45 minutes, and larger ones 60 minutes or slightly more until a fork or knife easily pierces through the flesh and the skin is crispy but not burnt. If the sweet potato is cut in half, the baking time is shorter, around 25 to 40 minutes depending on size. Start checking for doneness at the lower end of these times to avoid overcooking.

Summary:

• Whole small: 30-40 minutes
• Whole medium: around 45 minutes
• Whole large: 45-60+ minutes
• Halved sweet potato: 25-40 minutes

The potatoes should be placed on a baking sheet or directly on the oven rack, pierced with a fork several times before baking to prevent bursting, and baked until tender when squeezed or pierced.