Roast potatoes are the part of the meal everyone fights over, which makes running out a real problem. Too few and guests are disappointed. Too many and the oven is crowded, so none of them crisp properly. This free roast potato quantity calculator turns your guest count, crispness preference, and appetite into raw weight, oil, and tray count, so every potato gets its space.
Crispness changes the quantity because crispy potatoes are usually cut larger and eaten in bigger portions. A standard roast potato portion is about 250 grams of raw potato per person, while an extra crispy feast portion rises to about 320 grams. A light portion, for a meal with many other dishes, drops to about 200 grams. The calculator applies the setting you choose.
Using the tool is simple. Enter the number of guests, pick how crispy you want the potatoes, and choose the appetite level. Press Calculate roast potatoes and you will see the raw weight to buy, the oil needed, and how many roasting trays you need. The tray count assumes about one kilo of potatoes per tray, which is the key to crispness.
A worked example makes it clear. Four guests, standard roast potatoes, normal appetite: buy 1 kilo of raw potatoes, use 60 millilitres of oil, and use one tray. Eight hungry guests wanting extra crispy potatoes need 3.2 kilos, 192 millilitres of oil, and four trays. That sounds like a lot of trays, but it is the difference between golden and soggy.
Space in the pan is the secret most recipes understate. Potatoes crammed together steam instead of roasting, and no amount of hot oil fixes that. Spread them in a single layer with gaps between pieces, and use a second tray rather than overloading one. Turn them once halfway through cooking, and keep the oven hot and steady.
Oil quantity matters too, and the tool scales it with the potatoes. About one tablespoon of oil per 250 grams of potatoes gives a good coating without a greasy finish. Toss the parboiled potatoes in the oil with salt before they go in the tray, and preheat the oil in the tray so the potatoes sizzle the moment they touch it.
Choosing the right potato helps as much as the right amount. Floury varieties like Maris Piper or Russet crisp better than waxy salad potatoes, because their fluffy edges catch the heat. Parboil for about ten minutes, drain well, shake the pan to rough up the edges, and let the steam dry off before roasting.
These amounts are guides for typical tables, so adjust for your guests. A roast dinner crowd eats more potatoes than a summer lunch crowd, and children eat less. Start with the calculator result, watch what disappears first, and adjust next time. The tool is free, needs no sign-up, and runs entirely in your browser.
Scaling roast potatoes for a crowd needs one more plan: oven space and timing. Roast potatoes need high heat and air around them, so they cannot share a crowded oven shelf with a large roast and a tray of vegetables and still crisp properly. If your oven is small, roast the potatoes first, then hold them warm while the meat rests, since resting meat gives you twenty to thirty minutes of free oven time. For very large groups, use two oven shelves and swap the trays halfway through, so the lower tray gets its turn in the hotter upper heat. Goose fat or duck fat gives a richer flavour than oil and crisps beautifully, but vegetable oil works well too, and it keeps the dish suitable for vegetarian guests. Season generously with flaky salt after roasting rather than before, since salt drawn out during cooking can soften the crust, and add rosemary or garlic only in the last fifteen minutes, because both burn easily over a long roast. A squeeze of lemon at the end brightens the whole tray, though traditionalists may prefer them plain. If some potatoes are smaller than others, take the small ones out early so they do not burn while the large ones finish. Leftover roast potatoes reheat well in a hot oven for ten minutes, and they make excellent fried potatoes with onions the next morning. With the calculator for quantities and these habits for heat and space, roast potatoes stay golden, crisp, and plentiful.
Versión en español: Calculadora de Cantidad de Patatas Asadas – Peso Crudo por Invitado