Boiling potatoes typically takes about 15 to 20 minutes once the water has reached a boil. The exact time depends on the size and type of the potatoes. For example, smaller or cubed potatoes cook faster, usually around 10 to 15 minutes, while larger potatoes or waxier types may take up to 20 to 25 minutes or longer to become tender. Here is a general guide:

• Baby or small potatoes (about 1 to 2 inches): 12 to 15 minutes
• Medium potatoes (about 3 inches): 20 minutes
• Large potatoes (4 inches or more): 25 to 30 minutes

For sweet potatoes, the boiling time is about 20 to 30 minutes depending on size. Potatoes are done when they can be easily pierced with a fork and are fork-tender but not falling apart. Starting them in cold water and then boiling helps them cook evenly.