The maths behind the number
Every figure on this page comes from one line of arithmetic. Food composition tables report energy per 100 g, so multiplying that figure by your weight and dividing by 100 gives the calories in whatever amount you actually have.
A medium baked potato at 213 g, this page's default, works out to roughly 198 kcal from the potato alone: 93 kcal per 100 g, scaled up by 2.13. The same line converts to kilojoules by multiplying by 4.184, the standard factor between the two energy units, which is why the kJ figure sits right under the headline number rather than needing its own separate lookup.
Choosing a preparation and a weight
The four preparations above are not four different foods pretending to be one. Baked and boiled are the same potato, cooked two different ways; mashed is boiled potato with milk and butter worked back in; sweet potato is a genuinely different plant, included because its calorie count lands close enough to a white potato's to be worth a direct comparison. Picking one sets the per-100-gram figure that every other number on this page scales from.
The small, medium and large presets describe typical whole-potato weights for the size classes used across US grocery and foodservice charts, roughly 150 g, 213 g and 300 g. Potato sizing is genuinely inconsistent between one shop, one recipe and one restaurant portion and the next, so treat those three buttons as a sensible starting point rather than a promise. The slider underneath them moves freely from nothing up to 600 g, and switching the unit toggle to oz converts the same underlying weight rather than resetting it, so you can drag in whichever unit you think in and read the other one off without retyping anything.
The preparation ladder: an innocent potato, a guilty method
Sorted lowest to highest, the ladder runs boiled, sweet potato baked, white potato baked, mashed with milk and butter, then potato crisps a long way clear at the top. Boiled and baked sit only a handful of calories apart per 100 g, and the small gap between them is not really about the cooking method at all: the boiled figure on this page is peeled before cooking, while the baked figure keeps its skin, so the two rows differ by both variables at once rather than isolating either one. Mashed potato jumps up because milk and butter get worked back in after boiling, adding fat that plain boiled or baked potato never had. Potato crisps sit in an entirely different bracket again, at roughly 532 kcal per 100 g against 86 for boiled potato, a difference that comes almost entirely from the oil absorbed during frying rather than from the potato underneath it, which is why the chart marks crisps out as a separate outlier rather than folding it in with the rest.
The pattern across the whole ladder is the same one the diet advice above tends to skip: potato as a plant is a modest, high-water, high-fibre vegetable, and every large jump on this page traces back to what got added or how it was cooked, not to the potato changing its nature. That is a reason to read a menu or a nutrition label with more care, not a reason to treat potatoes themselves with suspicion.
What toppings really cost
Toppings are where a modest potato most often turns into a genuinely calorie-dense plate, and the honest fix is simply to see the number rather than guess it. A tablespoon of butter (14 g) adds roughly 100 kcal on the figures in this page's data (the USDA's own published reference for salted butter puts a level tablespoon at 102 kcal, a couple of calories apart depending on which composition table did the rounding). A matchbox-size piece of cheddar, about 30 g, adds a little over 120 kcal, and two tablespoons of sour cream add roughly 59 kcal. None of that makes a topping the wrong choice, a loaded baked potato can still fit comfortably into a day's eating, but stacking two or three of them onto one potato easily doubles its calories, and doing that without realising it is the more common problem than the potato itself.
Cooking and cooling: the resistant starch question
One genuinely interesting wrinkle sits underneath the calorie figures rather than in them. Cooking starch and then cooling it, a boiled potato left in the fridge overnight rather than eaten hot, converts some of that starch into a form called resistant starch, which digests more slowly and behaves more like fibre than like ordinary starch by the time it reaches the gut. A controlled study measuring the response directly found that chilled, previously cooked potatoes produced meaningfully smaller rises in blood glucose and insulin after eating than the same potatoes eaten hot, which is a real, measured effect rather than a diet myth. It does not change the calorie count on this page (the energy value of a food does not move much just because part of its starch has retrograded), and it is not a reason to eat potatoes cold if you would rather not: it is simply an honest example of how the same food can behave a little differently in the body depending on how it was handled after cooking, worth knowing rather than worth building a rule around.
Are potatoes actually fattening?
Potatoes have spent decades on the wrong side of diet advice, mostly guilt by association with butter, cheese, sour cream and deep frying rather than anything about the vegetable itself. The most useful correction comes from a 1995 study that built a Satiety Index by feeding people fixed 240-kcal portions of 38 common foods and tracking how full each one left them over the following two hours. Boiled potatoes came out on top of the entire list, more filling calorie for calorie than every other food tested, including wholemeal bread, porridge, apples, and steak. The likely reason is not magic, it is water and volume: a 240-kcal portion of boiled potato is a much larger, heavier serving than 240 kcal of most other foods on that list, and how much food actually fills your stomach turns out to matter more for fullness than which nutrients it happens to contain. None of that changes the arithmetic above, calories are still calories, but it is a genuine, measured reason a plain potato can be a useful, filling part of a calorie-controlled plate rather than something to avoid on principle.
Where these numbers come from
Every food row behind this calculator, the four preparations, the crisps comparison and all three toppings, comes from USDA FoodData Central's published composition tables for generic, home-prepared foods, not any single brand or restaurant. These are typical, verified figures for plain preparations; an actual potato you cook, or a topping you buy, will vary a little either side depending on variety, ripeness, exactly how much butter ended up on the knife, and how it was cooked. Treat every number on this page as a well-sourced estimate for planning, not a guarantee for one specific meal.
Questions people ask
How many calories are in a medium baked potato?
Around 198 kcal for a 213 g potato at 93 kcal per 100 g, before any toppings. That figure covers the flesh and skin baked plain; add butter, cheese or sour cream and the total climbs from there, shown separately in the toppings table above.
Why do boiled and baked potatoes have such similar calories?
Because cooking method is only part of what differs between the two rows on this page: the boiled figure is for peeled potato, while the baked figure keeps the skin on, so the roughly 7 kcal per 100 g gap reflects both the skin and the method mixed together rather than either one in isolation. Neither preparation adds fat, which is why both sit far below mashed or fried potato.
Is a potato actually fattening, or is that the toppings talking?
Mostly the toppings and the cooking method, not the potato. A plain boiled or baked potato is a modest, high-water vegetable; it is butter, cheese, sour cream and deep frying into crisps that turn it into something calorie-dense, exactly the jump the preparation ladder above is built to show.
Does cooking and cooling a potato really change how it affects blood sugar?
Yes, measurably. Cooling cooked potato converts some of its starch into resistant starch, and a controlled study found chilled, previously cooked potatoes produced smaller rises in blood glucose and insulin than the same potatoes eaten hot. It is a real effect on how the starch behaves in digestion, not a change to the calorie count itself.
Are potato crisps really that much worse than a potato?
By calories, yes, by a wide margin: roughly 532 kcal per 100 g against 86 for boiled potato, over six times as much. The difference is almost entirely the oil absorbed during frying rather than anything about the potato itself, which is exactly why crisps sit apart from the rest of the ladder rather than blending in with the cooked preparations.
Why might my app or a packet show a different calorie figure?
Different composition tables round slightly differently, and any real potato, or any real tub of butter, varies a bit from the generic USDA figures this page uses. A gap of a few calories per 100 g between two honest sources is normal; a gap of several hundred usually means one of you is looking at a different preparation, brand or portion size.
This tool applies published, generic USDA composition figures to the weight and preparation you choose; it is not a substitute for weighing your own food or reading a specific product's label, and it is not medical or dietetic advice.