How this calculator works
Cooking area, not the number of burners, decides how many people a grill can serve at once. The common planning figure is 72 square inches per person, about 465 cm2, roughly the area of a dinner plate. It assumes one round of food cooked together, which suits burgers, sausages or steaks for a crowd. Two things move the number: a two zone setup, where part of the grate is kept cooler for finishing, halves the usable area, and cooking in batches means the second batch eats later. A round grill is measured by its diameter and a rectangular one by its length and width, but only the main grate counts. Warming racks and side shelves are not cooking surface and should not be added to the total.
Formula
needed area = people x 465 cm2. rectangle area = length x width. round area = pi x (diameter / 2)^2. difference = your area - needed area. The equivalent round diameter for a needed area is 2 x square root(area / pi).
Worked example
For 10 people the needed area is 10 x 465 = 4650 cm2, or about 721 square inches. A rectangular grill 60 cm by 40 cm has 2400 cm2, which is 2250 cm2 short, so it would need two rounds of cooking. A round grill 80 cm across has pi x 40^2 = 5027 cm2 and enough room. Spreading 2 kg of meat over 10 people gives 200 g each, before any loss to fat and drips.
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Frequently asked questions
Should I size the grill by people or by food?
Both matter. The area per person figure assumes one plate of food each, cooked at once. If you are cooking a large roast or a whole fish, the shape of the item may need more room than the headcount suggests, so compare the needed area with the size of the food as well.
Does a lid or a warming rack change the answer?
A lid lets you cook with indirect heat, which is useful for larger cuts, but it does not add usable grate area. A warming rack holds cooked food rather than cooking it, so count only the main grate when you compare grills.
How much meat should I buy?
About 200 to 250 g of raw meat per adult is a generous main course, with less for children and more if there are few other dishes. Buns, salads and sides reduce the meat needed, and a single 2 kg joint feeds a crowd differently from the same weight of sausages.
Is 72 square inches per person a rule I must follow?
It is a planning guide from grill makers and barbecue writers, not a safety requirement. It gives comfortable spacing for turning food. If you are happy cooking in two batches, or serving one item at a time, a smaller grill will do.