Calculating the cubic feet of cylindrical ducting

MFL

Member
I’m not sure who needs to know this, but if you need to know the volume of air in your intake/exhaust ducting look no further. Here’s an example with a 6” diameter exhaust duct that’s 25’ long.

Step 1: take the radius of your duct which is half the diameter, 3 in this case and square it (3x3), bringing us to 9”.
Step 2: multiply 9 by 3.14 (pi), 28.27
Step 3: multiply it by the length of your duct, 25 in this case, and you’ll have the cubic inches of 706.85.
step 4: Divide that by 12 to get to feet and you’ll find that the duct holds 58.9 cubic feet of air.
 
I’m not sure who needs to know this, but if you need to know the volume of air in your intake/exhaust ducting look no further. Here’s an example with a 6” diameter exhaust duct that’s 25’ long.

Step 1: take the radius of your duct which is half the diameter, 3 in this case and square it (3x3), bringing us to 9”.
Step 2: multiply 9 by 3.14 (pi), 28.27
Step 3: multiply it by the length of your duct, 25 in this case, and you’ll have the cubic inches of 706.85.
step 4: Divide that by 12 to get to feet and you’ll find that the duct holds 58.9 cubic feet of air.
Step 4, divide by 144. :wink:
 
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