BBQ cooking area explained: cm², grill diameter and burgers

Primary area and total area

The primary cooking area is the main grate directly over the heat. Total cooking area often adds warming racks, upper shelves or side burner grates. Both figures are useful, but only the primary area tells you how many burgers you can cook at once. A warming rack holds buns and cooked food, and it suits indirect cooking, but it is not where you sear.

The Kenmore 3-burner grill's listing shows the difference well: 512 sq in combined, of which 381 sq in is the primary surface and 131 sq in a warming rack. The Royal Gourmet offset smokers list 811 sq in in total, made up of 443 sq in of main grates, a 184 sq in warming rack and a 184 sq in firebox grate.

Converting square inches and grill diameters

To convert square inches to square centimetres, multiply by 6.45. To go the other way, divide by 6.45. For a round grate, area is pi x radius squared, or about 0.785 x diameter squared. Kettle and kamado sizes are usually given as the grate diameter in cm or inches.

Makers' own figures can differ slightly from the maths because the usable grate is a little smaller than the bowl. Weber lists 2,342 cm² for its 57 cm Original Kettle, close to the theoretical figure.

How many burgers per 1,000 cm²

A 10 cm burger covers about 80 cm², but you need space to slide the spatula in and turn it, and the edges of a grill are cooler. Makers' figures suggest about 140 to 200 cm² per burger: Weber says nine fit on the 1,290 cm² Q 1200N and 12 on the 57 x 41 cm Q 2200N. That works out at roughly five to seven burgers per 1,000 cm².

Sausages take less room each, chicken pieces and steaks more. For mixed food, plan by burgers and you will be close. Our food per person guide turns this into grill sizes for parties.

Rectangular grills: reading the figures

For gas and pellet grills, the grate is usually given as width x depth. Multiply them for the area: the Weber Traveler's 63 x 34 cm grate gives 2,142 cm² by maths, listed as 2,065 cm². The CosmoGrill Pro Deluxe's 77 x 42 cm grate gives about 3,234 cm², listed as 3,214 cm².

Watch for obvious errors in online listings, such as a large six-burner grill shown with 92 cm². When a figure looks wrong, use the stated grate dimensions or the maker's own spec sheet. Our guides mark these cases rather than guessing.

Using cooking area to choose a BBQ

Pick a grill whose primary area lets you cook for about a third of your usual guests at once, and add a warming rack if you entertain. For two to four people, around 1,300 cm² is plenty; for a family of four to six with guests, aim for 2,000 to 2,500 cm²; for big parties, 3,000 cm² or more. Remember that bigger grills need more space and more fuel to heat.

Compare models by stated area in best gas BBQs for UK gardens, best charcoal BBQs and large gas BBQs for family parties.

Compare charcoal BBQ sizes →

Frequently asked questions

How many people does a 57 cm kettle feed? Weber says six to eight people for its 57 cm Original Kettle, cooking in a couple of batches.

Does cooking area include the warming rack? Often yes for total area. Look for the primary area figure, or check the grate dimensions.

How do I convert square inches to cm²? Multiply by 6.45. For example, 443 sq in is about 2,858 cm².

Is a bigger cooking area always better? No. A large grill takes longer to heat, uses more fuel and needs more space. Buy for your usual numbers, not the one big party a year.