use charcoal...
The normal formula is to use twice the number of briquettes as the diameter of the oven. For a 12 inch oven, you would use 24 briquettes. Depending on the type of cooking you are doing, you need to make the heat come more from the top or bottom of the oven. For example, too much heat on the bottom will burn bread.
To do this, you place more or less of the briquettes on the lid.
Here is a simple chart:
Baking
More heat from top so bottom does not burn.
Place 3/4 coals on top and 1/4 underneath.
Roasting
Heat comes equally from top and bottom.
Place 1/2 coals on top and 1/2 underneath.
Stewing, Simmering
Most heat from bottom.
Place 1/4 coals on top and 3/4 underneath.
Frying, Boiling
All head from bottom.
Place all coals underneath.
Most baking recipes require a temperature setting of 325ºF. An easy method to get a temperature of 325ºFahrenheit within your Dutch oven is to subtract or add the number 3 to the size of your Dutch oven to determine the number of charcoal briquettes to use underneath and on top. Find the size of the Dutch oven you use (see chart below) to know the correct number of briquettes.
Dutch Oven 325° Temperature — Briquette Quantities Size of Oven Top Bottom
8-inch 11 5
10-inch 13 7
12-inch 15 9
14-inch 17 11
16-inch 19 13
The following example uses the formula for a 12-inch Dutch oven.
* Subtract 3 from 12, which equals 9 — the number of briquettes to place beneath the oven.
* Take the number 12 and add 3, which equals 15 — the number of briquettes to place on the lid of the oven.
With this formula, 9 briquettes go underneath and 15 briquettes are placed on the top of the lid of a 12-inch Dutch oven to cook at 325ºF. One-third of the heat will be underneath the Dutch oven, and two-thirds of the heat will be on top. Heat rises, so you do not need as many coals on the bottom of the oven.
Arrange briquettes so they are evenly spaced under the Dutch oven and on its lid. Also, you always need to rotate your Dutch oven a quarter turn every 15 minutes to avoid hot spots. Replace briquettes with new coals as they burn out.
Temperature control is determined by charcoal briquette placement
Rule of 3
This is a real simple estimate of briquettes. Take the dutch oven diameter and add 3 briquettes on top. Subtract 3 briquettes underneath. So, a 12 inch oven would have 12+3=15 on top and 12-3=9 underneath. This works for any size dutch oven. Then you need to adjust briquette placement depending on the type of cooking.
Rings of Coals
As it turns out, the sizes of briquettes work out so that the recommended briquettes count above can be estimated easily. As an experiment, you can take a 12 inch dutch oven and 24 briquettes. On the lid, make a ring of briquettes all the way around the outer edge. How many did you use? I bet it was 15 or 16!
Now, see how many it takes to make a ring just under the oven. There should be 3 or 4 briquettes between each leg for a total of 9 to 12.
That is pretty close to the recommendation for a 350 degree roasting set up, isn't it? It works pretty well for any size dutch oven and any size briquettes - smaller briquettes means you need more of them, but its about the same amount of burning mass to make a ring!
A ring around the top and the bottom is about 325 to 350 degrees.
Remove every other briquette underneath to make 300 degrees.
Add a second ring to the top to make 375 degrees.
If your camp cooking calls for stewing or frying, you'll want to drop most of those top coals down and shove them under the oven. If you're baking breads, then maybe move a couple from underneath up to the top.
Just remember that a ring around the top and a ring around the bottom is your base starting point and tweak it from there.
Oh, I forgot to mention that this is exactly how I do it with real wood coals. Since coals are irregular and you can't count them, I put a