Roast Potato Calculator
Tell us how many you are feeding for the quantity to buy, the parboiling time and the roasting time.
Answer
1 kg of potatoes
What to do
- 1Peel and cut 1kg of floury potatoes (Maris Piper or King Edward) into pieces about the size of a small egg.
- 2Parboil in salted water for 8 minutes from boiling, then drain them very well.
- 3Put the lid on the pan and shake it hard. Those roughed-up edges are what turn crisp.
- 4Heat 3 tablespoons of goose fat, beef dripping or oil in the roasting tin in the oven until it is properly hot.
- 5Roast at 220°C for 50 to 60 minutes, turning them at 30 minutes.
Your numbers
Next step
Source: Food Standards Agency, Cooking your food: cooking temperatures and times (GOV.UK) · Reviewed 2026-09-11 · Guidance version 2.0.0
Reference and detail
Why parboiling matters
Parboiling then roughing up the edges is the whole trick. Those broken surfaces are what turn into the crisp, craggy edges. Skip the parboil and you get a potato that is smooth, pale and disappointing.
Hot fat, hot tin, space around each one
The fat must be shimmering hot before the potatoes go in, and each potato needs air around it. Crowd the tin and they steam. Two tins with room beats one tin packed tight, every time.
Fitting them around the joint
Roast potatoes want 220°C and most joints want 180°C. The usual answer is to roast the meat first, then rest it under foil for 20 to 30 minutes while the potatoes get the oven to themselves at full heat. The Meal Synchroniser works this out for you if you add both dishes.
Questions and answers
More questions about roast potatoes
Which potatoes roast best?
Floury varieties such as Maris Piper and King Edward give the fluffiest middles and the craggiest edges. Waxy salad potatoes hold their shape but never develop the same crisp, broken surface.
What fat should I roast potatoes in?
Goose fat, beef dripping or a neutral oil such as sunflower or vegetable all work well because they can be heated very hot without burning. Olive oil has a lower smoke point and can taste bitter if the tin is as hot as roast potatoes need.
How many potatoes should I buy per person?
This depends on whether they are a side or the main starch on the plate, so use a dedicated calculator for the raw weight to buy.
Can I parboil and rough up roast potatoes in advance?
Yes, parboil and rough them up, then cool and refrigerate them, covered, until you are ready to roast. Cool them quickly before chilling and only reheat the cooked potatoes once.
Food safety
Cooking times are a guide only. Ovens, joints and starting temperatures vary, so always check the food is cooked before serving rather than relying on the clock.
Source: Food Standards Agency, Cooking your food: cooking temperatures and times (GOV.UK) · Reviewed 2026-09-11 · Guidance version 2.0.0
Safety guidance reviewed against Food Standards Agency sources on 11 September 2026. How we calculate cooking times and safety guidance.