Installation Guide
5
Duct  pieces 
To tal
Equivalent  number
length  x used   =
3- 1/ 4” x 10”
Rect.,
straight
1 Ft.  x (  )  =
Ft.  
3- 1/ 4” x 10”
Rect. to
6” round
transition
5 Ft.  x (  )  =
Ft.  
3- 1/ 4” x 10”
Rect. to
6” round
transition
90
0 
elbow
20 Ft.  x (  )  =
Ft.  
6”, 7”, 8”, 10” 
Round,
90
0 
15 Ft. 
x (  )  =
Ft.  
6”, 7”, 8”, 10”
Round,
45
0 
9 Ft.  x (  )  =
Ft.  
Ft.  
6”, 7”, 8”, 10” 
Round,
straight 
1 Ft.  x (  )  =
Ft. 
Subtotal column 1 =
Duct  pieces 
To tal
Equivalent  number
length  x used   =
6”, 7”, 8”, 10”
Round, wall 
cap with 
damper 
30 Ft.  x (  )  =
Ft. 
Ft.  
Ft.  
Ft.  
6”, 7”, 8”, 10”
Round
roof cap 
30 Ft.  x (  )  =
Ft.  
Subtotal column 2 =
Subtotal column 1 =
Total ductwork  =
Maximum Duct Length: For satisfactory air movement,
the total duct length       
should not exceed 100 equivalent feet.
6” round to
3- 1/ 4” x 10”
rect. 
transition
1 Ft.  x (  )  =
Ft.  
6” round to
3- 1/ 4” x 10”
rect. 
transition
90
0 
elbow
16 Ft.  x (  )  =
Ft.  
7” round to
3 1/ 4” x 10”
rect. 
transition
8 Ft.  x (  )  =
Ft.  
7” round to
3- 1/ 4” x 10”
rect. 
transition
90
0 
elbow
23 Ft.  x (  )  =
Ft.  
elbow
elbow
7” to 6” or
8” to 7” Round 
tapered 
reducer
25  Ft.  x (  )  =
Ft. 
3- 1/ 4” x 10”
Rect. 90
0
elbow
15 Ft.  x (  )  =
Ft.  
3- 1/ 4” x 10”
Rect. 45
0
elbow
9 Ft.  x (  )  =
Ft. 
3- 1/ 4” x 10”
Rect. 90
0
flat elbow
24 Ft.  x (  )  =
Ft. 
3- 1/ 4” x 10”
Rect.
wall cap
with damper
30 Ft.  x (  )  =
Ft. 
 Ft.  x (  )  =
Ft. 
15
6”, 7“, 8”
Round 
in-line 
damper
Installation – Ducting Calculation Sheet










