How Long to Boil Sweet Potatoes (Cubes or Whole)

Boil sweet potatoes cut into 1-inch chunks for 20 to 30 minutes, until a fork goes in with no resistance. Whole sweet potatoes in their skins take considerably longer and are best tested with a knife rather than a timer, starting at about half an hour. Purdue Extension’s instruction for mashing is to dice them into chunks and boil for 20 to 30 minutes, until tender when poked with a fork.

The size of the cut is what decides the time, and the skin decides the flavour. Both are worth two minutes of thought before you fill the pan.

Boiling times by cut

Cut	Time in boiling water
1/2-inch dice	12–15 minutes
1-inch chunks	20–30 minutes
Thick rounds or halves	25–35 minutes
Whole, medium, skin on	from about 30 minutes, test with a knife
Whole, large, skin on	45 minutes or more

Sweet potatoes are not like pasta — a couple of extra minutes will not ruin them, and undercooking is the more common mistake. If a fork meets any resistance at all in the middle, they are not done, and they will not mash smoothly.

Cook them in their skins

This is the one instruction that changes the result most, and it comes straight from the University of Arkansas extension service: when boiling sweet potatoes, cook them in their jackets, which “will prevent some of the sweetness from being dissolved in the water”, and the skin then peels off easily, taking less of the potato with it.

Peeled cubes boiled naked lose sugar and colour to the water — you can see it, because the water goes orange. Skin-on takes longer, but it is the version that tastes of something. If you are cubing them for speed anyway, leave the skin on the pieces: it is edible, it holds the cubes together in the pan, and the University of Nebraska’s food team notes that leaving the skins on gives a different texture and more fibre.

The method

Scrub them properly. They come out of the ground, so the skins need a brush even when they look clean.
Start whole potatoes in cold water; start cut pieces in boiling water. A whole potato in boiling water cooks a soft ring on the outside long before the middle gives.
Salt the water and keep the pan at a steady boil, not a violent one — a hard boil knocks cut pieces into mush at the edges.
Test with a thin knife, not a fork, on whole potatoes. A knife slides through a cooked one with no grip at all.
Drain them and let them steam dry in the empty pan for a minute before mashing. Wet sweet potato mash is the most common thing to go wrong here, and it is entirely a draining problem.

For mashing

Sweet potato mash needs less liquid than you think, because the potato holds so much of its own. Drain thoroughly, mash while very hot, and add butter before any milk — the fat coats the starch and stops it going gluey.

If it is still loose, put the pan back on a low heat for a minute and stir; the steam that comes off is the water you do not want in the dish. Our potato quantities chart works for sweet potatoes as well as white ones when you are scaling mash for a table.

When boiling is the wrong method

Boiling is fast, easy to time and the right call for mash, soup and anything going into a stew. It is the wrong call when you want the flavour concentrated, because water pulls sugar out rather than caramelising it.

For that, cook them dry:

Baked whole: the University of Nebraska’s method is to pierce the skin several times and bake at 400°F for 40 to 50 minutes, or until fork-tender. Arkansas goes hotter — 450°F for about 45 minutes — and says not to wrap them in foil, which steams them instead of roasting them.
Microwaved whole: pierced, on a plate, 5 to 8 minutes, rotating halfway. Both extension services give the same window, and it is genuinely the fastest hot vegetable in the house on a school night.
Roasted in chunks: the version most likely to be eaten by a child who says they do not like sweet potato, for the same reason roasting works on boiled broccoli sceptics.

Buying and storing them

Store them somewhere cool, dark and dry, and not in the fridge. Arkansas is blunt about this: refrigeration “can slow sprouting but causes the starch to convert to sugar”, giving you a hard centre and an off taste. Purdue puts short-term storage at three to five weeks in a cool dark spot.

Sweet potatoes for the freezer are a different job again. The National Center for Home Food Preservation’s method is to cook them until almost tender first, cool, peel and then slice or mash, packing with half an inch of headspace — and to keep mashed sweet potato from darkening, to mix in 2 tablespoons of orange or lemon juice per quart. Raw sweet potato does not freeze, in the same way and for much the same reason that raw white potatoes do not.

Sweet potato as a first food

Boiled sweet potato is one of the standard starting foods for babies, and the reason is mechanical rather than nutritional: boiled soft and mashed thin, it is smooth without a skin, a seed or a string in it, and it thins down with milk or the cooking water to whatever consistency a new eater can manage. Boil it plain — no salt, no butter — and season the adults’ portion separately in the bowl.

If you are at the stage of working out what goes in the bowl first, Betteroo’s guide to getting started with purées covers textures and timing; the cooking half is just this page with the salt left out.

Frequently asked questions

How long do you boil sweet potatoes? 20 to 30 minutes for 1-inch chunks, and about 12 to 15 for a small dice. Whole ones in their skins take from half an hour and should be tested with a knife.

Should you peel sweet potatoes before boiling? No. Cooking them in their skins keeps the sweetness in the potato rather than in the water, and the skin slips off easily once they are cooked.

How do you know when a sweet potato is done? A thin knife goes into the thickest part with no resistance. If there is any grip in the middle, give it another five minutes.

Can you boil sweet potatoes ahead of time? Yes. Boil, drain, cool and refrigerate them whole or in chunks, then reheat in a covered dish or mash them straight from cold with hot milk and butter.

Do sweet potatoes take longer than regular potatoes? Cut to the same size, they are broadly similar — the timings are close to those in our baby potato boiling guide. Whole sweet potatoes are often bigger and denser, which is where the extra time comes from.

Why is my sweet potato mash watery? It was not drained and dried properly. Return the drained potatoes to the hot empty pan for a minute to steam off the surface water before you mash them.