Formula to calculate gas furnace airflow: CMF = ((Input * Efficiency) / (1.08 * Temperature Rise))

80% Efficient Furnace
Input
Temp. Rise 50,000 75,000 100,000 125,000 150,000
20 1,852 2,778 3,704 4,630 5,556
25 1,481 2,222 2,963 3,704 4,444
30 1,235 1,852 2,469 3,086 3,704
35 1,058 1,587 2,116 2,646 3,175
40 926 1,389 1,852 2,315 2,778
45 823 1,235 1,646 2,058 2,469
50 741 1,111 1,481 1,852 2,222
55 673 1,010 1,347 1,684 2,020
60 617 926 1,235 1,543 1,852
65 570 855 1,140 1,425 1,709
70 529 794 1,058 1,323 1,587

90% Efficient Furnace