Quick answer: diced potatoes take 10 to 15 minutes from the point the water reaches a simmer. Whole medium potatoes take 15 to 20 minutes, and whole large russets up to 30. Two things matter more than the timer: start them in cold water, not boiling water, and pick the right variety, because the potato that makes fluffy mash is the wrong one for potato salad.
Boiling Times by Cut and Size
All times are counted from when the water reaches a gentle simmer, not from when you turn the hob on. That distinction alone accounts for most of the conflicting numbers you will find online.
| Cut | Time from simmer | Best for |
|---|---|---|
| Diced, 2 cm cubes | 10 to 15 minutes | Mash, potato salad, curries, hash |
| Diced small, 1 cm | 7 to 10 minutes | Quick salads, adding to soup late |
| Quartered medium potatoes | 15 to 20 minutes | Roasting after par-boiling, mash |
| Whole baby or new potatoes | 15 to 20 minutes | Potato salad, buttered new potatoes |
| Whole medium, roughly 150 g | 20 to 25 minutes | Salads where you want to peel after |
| Whole large russet or baking potato | 25 to 30 minutes | Mash, when you want minimum waterlogging |
The doneness test: slide the tip of a small knife into the thickest piece. It should go in with almost no resistance and the potato should slip off the blade when you lift it. If the potato clings to the knife, give it two more minutes. Test one of the largest pieces, not a convenient one near the edge.
Start in Cold Water, and Why It Matters
This is the single most useful technique on this page, and most quick answers skip it.
Put the potatoes in the pan, cover them with cold water by about 2 cm, then bring it up to heat. If you drop potatoes into water that is already boiling, the outside cooks and begins to break down long before the middle is done, and you get pieces that are simultaneously mushy at the edges and firm in the centre. A cold start lets the whole piece come up to temperature together.
The larger the piece, the more this matters. For 1 cm dice it makes little difference. For whole potatoes it makes all the difference.
- Salt the water. Roughly a teaspoon per litre. Potatoes are bland and season poorly after cooking, so this is your one chance to get seasoning inside them.
- Simmer, do not hard boil. A rolling boil knocks the pieces against each other and rounds off the edges, which matters most for salad.
- Cut evenly. Uneven dice is the most common reason a batch comes out half mushy and half hard.
- Cover the pan to reach the simmer faster, then leave the lid ajar so it does not boil over.
Mash Versus Salad: Use Different Potatoes
Here is the thing that determines your result more than the timing does. Potatoes divide into two broad types based on starch content, and they behave in opposite ways.
| Floury or starchy | Waxy | |
|---|---|---|
| Varieties | Russet, Maris Piper, King Edward, Idaho | New potatoes, baby potatoes, Charlotte, red-skinned varieties |
| What they do when boiled | Cells separate, texture goes fluffy and dry, edges break down | Cells hold together, pieces keep their shape and a firm bite |
| Use for | Mash, roasting, baking, chips | Potato salad, gratins, curries, anywhere the shape must survive |
| What goes wrong if you swap | Floury potatoes in salad collapse into a mush when you dress them | Waxy potatoes make gluey, heavy mash no matter how you treat them |
All-rounders such as Yukon Gold and Desiree sit between the two and work acceptably for both, which is a reasonable choice if you only want to buy one bag.
For mash
- Boil in larger pieces, or whole, so less water gets in. Waterlogged potatoes make watery mash.
- Drain thoroughly, then return to the dry hot pan for a minute to steam off the surface moisture.
- Warm the milk or cream before adding it. Cold liquid firms the starch and dulls the texture.
- Do not use a blender or food processor. Overworking ruptures the starch cells and turns mash into glue. A masher or a ricer, and stop as soon as it is smooth.
For potato salad
- Waxy varieties, cooked whole where possible and cut after, so fewer cut surfaces absorb water.
- Pull them slightly earlier than you think, since they carry on cooking briefly after draining.
- Dress them while still warm. Warm potatoes absorb dressing and vinegar; cold ones just get coated. This is the difference between a good potato salad and a bland one.
- A splash of vinegar or lemon on the warm potatoes before the mayonnaise goes in adds a lift most home versions lack.
Peel Before or After?
Boiling with the skin on keeps more of the fibre, potassium and vitamin C in the potato rather than in the cooking water, and it also stops the flesh absorbing as much water. The skins slip off easily once cooked and cooled slightly.
Peeling first is quicker and gives a cleaner result for mash, at the cost of some nutrients and a slightly wetter potato. For salad, skin-on is usually both easier and better looking.
Storage and Safety
- Cooked potatoes keep three to four days in the fridge in a covered container.
- Cool them within two hours and refrigerate. Do not leave cooked potatoes at room temperature overnight, and do not leave a foil-wrapped baked potato out. Cooked potatoes left warm are a recognised setting for Clostridium botulinum growth, which is rare but serious.
- Raw potatoes do not belong in the fridge. Cold storage converts starch to sugar, which affects flavour and browning. Keep them somewhere cool, dark and dry with air circulation.
- Green patches and sprouts. Green skin indicates solanine, a natural toxin that is not destroyed by boiling. Cut green areas and sprouts away generously, and discard any potato that is extensively green or tastes bitter.
- Peeled potatoes brown quickly. Hold them in cold water for up to a day in the fridge if you are prepping ahead.
Nutrition, Briefly
A medium baked potato with the skin, around 173 g, supplies roughly 161 calories, 4.3 g protein, 36.6 g carbohydrate, 3.8 g fibre and almost no fat. It is a useful source of potassium, vitamin C and vitamin B6, and most of the fibre sits in or just under the skin.
Two things worth being accurate about, because they are widely overstated in both directions:
- Potatoes do not prevent heart disease, and no single food does. They fit into a heart-healthy pattern; they do not create one. See our heart-healthy eating guide for what the evidence actually supports.
- Potatoes are not off-limits with diabetes. They are a high-glycaemic-index food, so portion size, what you eat alongside them, and the cooking method all affect the blood glucose response. Interestingly, cooling boiled potatoes increases their resistant starch, which lowers the glycaemic impact — one reason potato salad behaves differently from hot mash. Anyone managing diabetes should follow their own dietitian’s advice rather than a general article.
For a fuller breakdown, see our mashed potato nutrition guide and sweet potato nutrition facts.
Common Mistakes
| Problem | Cause | Fix |
|---|---|---|
| Mushy outside, hard middle | Started in already-boiling water, or pieces cut unevenly | Cold-water start, even dice |
| Watery mash | Small pieces absorbed water, or not drained properly | Bigger pieces, then steam-dry in the hot pan |
| Gluey mash | Waxy potatoes, or overworked with a blender | Floury variety, masher or ricer, stop early |
| Potato salad falls apart | Floury variety, or boiled too hard | Waxy variety, gentle simmer, pull slightly early |
| Bland potatoes | Unsalted cooking water | Salt the water properly before cooking |
| Grey or dark patches after cooking | Natural oxidation, harmless | A splash of vinegar or lemon in the water reduces it |
Frequently Asked Questions
Diced potatoes cut into roughly 2 cm cubes take 10 to 15 minutes from the moment the water reaches a simmer. Smaller 1 cm dice takes 7 to 10 minutes. Test the largest piece with the tip of a knife: it should slide in with almost no resistance and the potato should fall off the blade.
Cold water, covering them by about 2 cm, then bring the pan up to heat. Dropping potatoes into already-boiling water cooks the outside long before the centre, giving pieces that are mushy at the edges and firm in the middle. The larger the pieces, the more this matters.
Use floury or starchy varieties such as russet, Maris Piper or King Edward for mash, because their cells separate into a light, fluffy texture. Use waxy varieties such as new potatoes, baby potatoes, Charlotte or red-skinned types for salad, because they hold their shape. Swapping them is why salads collapse and mash turns gluey. Yukon Gold and Desiree are reasonable all-rounders.
Cut them smaller, since 1 cm dice cooks in about half the time of whole potatoes, and keep the lid on while the water comes up to temperature. Use only enough water to cover them by a couple of centimetres, since a smaller volume heats faster. Do not compensate by boiling harder, which damages the texture without saving meaningful time.
Two usual causes. Either you used a waxy potato, which holds its cells together and resists mashing into a fluffy texture, or you overworked it with a blender or food processor, which ruptures the starch cells and releases starch. Use a floury variety and a hand masher or ricer, and stop as soon as it is smooth.
Skin-on retains more fibre, potassium and vitamin C, since fewer nutrients leach into the water, and the flesh absorbs less water. The skins slip off easily once cooked and slightly cooled. Peeling first is quicker and gives a cleaner mash, at the cost of some nutrients and a slightly wetter result.
Three to four days in a covered container in the fridge. Cool them within two hours of cooking rather than leaving them out, because cooked potatoes held warm for long periods are a recognised setting for bacterial growth. Raw potatoes should not be refrigerated, since cold converts their starch to sugar and affects both flavour and browning.
Cut green patches and sprouts away generously, since green colouring indicates solanine, a natural toxin that boiling does not destroy. Discard any potato that is extensively green, heavily sprouted or tastes bitter. A few small sprouts on an otherwise firm potato can simply be removed.
Sources
- USDA FoodData Central, for potato nutrient values.
- FoodSafety.gov — Cold Food Storage Chart.
- US Food and Drug Administration — Refrigeration and food safety.
- MedlinePlus — Green potato and solanine poisoning.
- NHS — How to store food safely.
Last updated: August 2026. Nutrition figures are general reference values and vary with potato size and variety. If you are managing diabetes, kidney disease or another condition where carbohydrate or potassium intake matters, follow the advice of your doctor or dietitian rather than general guidance.
