air inlet/damper size

[gsuders86]

Going to have a 16x16 firebox door. Firebox will be 18x18x16 (Cinderblock lined with fire brick). Thinking of making air inlets/dampner with circle steel plates. One at the top and one at the bottom of the door. How many and what size should the holes be? Is there a general rule of thumb that your inlnet/damper size should be x amount of the size of your firebox?

 

[Chasdev]

Can't help with that math but I can offer up that many people choose to run with the firebox door and exhaust damper wide open and control the cook grate temp through regulation of the size of the fire.
That's for wood, charcoal only probably requires adjustment to airflow.