gas flow rate.

If raining like cats and dogs and over 24 hr , how much rain has fallen?

Same your question. What Btuh/Kw burner?

As the question was set the capacity of the burner is of no interest. What is of interest is the AREA of the orifice/nozzle the gas flows thriugh into the burning cavity. This because flow is, within some limits, proportional to (Δp)^0.5.