Air Flow Through Orifices

Volume of free air in CFM that will flow thru round holes from a receiver into the atmosphere. Cubic feet of air per minute measured at absolute pressure of 14.7 lbs. per sq. in. and 70¼ F.

Guage Pressure in Reciever – Pounds
Dia. of Orifice
(In.)
2510152025303540455060708090100125150200
1/640.040.0620.0770.1050.1230.140.1580.1760.1940.2110.290.2670.30.3350.370.4060.4940.5830.75
1/320.1580.2480.3110.420.4910.5620.6330.7030.7740.8450.9161.061.21.341.481.621.982.323.18
3/640.3560.5680.7120.9441.11.261.421.581.751.912.062.382.733.333.664.445.256.86
1/160.6330.9931.241.681.962.252.532.813.13.383.664.234.795.365.926.497.99.112.17
3/321.432.232.83.784.415.055.696.3177.638.259.510.81213.314.617.820.927.35
1/82.533.974.986.727.868.9810.111.312.413.514.716.919.221.423.72631.637.348.7
3/165.78.9311.215.217.6520.222.825.22830.5333843.248.353.258.57184109.6
1/410.115.919.926.931.435.940.54549.654.158.667.676.785.794.8104126149.3195
3/822.835.744.760.570.780.991.1101112122132152173193213234284336438
1/240..563.579.6108126144162180198216235271307343379415506596777
5/863.0399.3124.51681962252532813103383664234795365926497909321216
3/491.2143179.2242283323365405446487528609690771853934113813401750
7/8124195244.2329385440496551607662718828939105011611272154918252382
1162254318.243050357564872079386593810821227137115161661202323853112
1 - 1/8205321402.554463772782091010041094118713701552173419182101256030203940
1 - 1/42533974986727849001019112412401352146416931917214423702596316037254860
1 - 3/830748260481695410911230136715051643178020542330260728803153384045255910
1-1/2364572716968113212931460162017831946211223352760308134123734455053607000
1 - 3/44967809721318154017601985220524292650287533103755420046455085619573009530
264810151274172021202300259428803173346037524330491554806070665081009540124

Table is based on 100% coefficient of flow. For well rounded entrance, multiply values by 0.97. For sharp edge orifices, a multiplier of 0.65 may be used. This table will give approximate results only. The formula Q=14.5 PD2, where Q is CFM, P is absolute pressure and D is orifice diameter in inches, may be used for any points not given in table. (Applies only above 15 pounds gauge.)