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Dear customers & visitors, as Microsoft is closing down its SharePoint soon, .TT pocketEngineer softDesign is relocating its home to Google site at
 Ductulator Plus+ v1.15 - HVAC duct sizing


the ultimate "mobile" duct sizer for Windows desktop/laptop PC



To take a glance at all pocketEngineer software and OS requirements, click Overview.

For Android OS, see aDuctulator.


 Note: Ductulator Plus (Windows) and aDuctulator (Android) are not the same. 


 Ductulator Plus: HVAC Duct Sizer on-the-go  

Ductulator Plus, a duct sizing calculations program for Windows PC,  is specially designed by a professional engineer to replace the conventional hand-held ductulator. It helps you to do duct sizing in a quick and flexible way according to equal friction, velocity, and duct dimensions methods.

Aim: creating a mobile design environment (
ShowMe!) for the practising HVAC engineers & designers in today's mobile world.

Results: Instant solutions at your fingertips.



 Built-in Features Highlights . . .

 Duct sizing for Rectangular, Round or Oval shape with 3 common sizing methods (i.e., equal friction, velocityby duct dimensions or find Airflow). Detail results such as velocity pressure, hydraulic diameter, reynolds number, friction factor, relative roughness and flow area are included.
 Rectangular and Oval duct sizes are obtained by direct iteration algorithm method, i.e., not converted from round duct size.
 full control and exact on input parameters, i.e., no sliding bar type of input method which can be difficult to control to exact numbers.
 different duct materials selection (Galv. steel, Spiral, Aluminium, Carbon steel, PVC, Duct board, Duct liner, Flexible duct and Concrete).
 find duct fictional loss rate by Duct Dimension method (useful design tool for existing duct).
 built-in Duct Converter, rhoAIR, Louvre Sizer, Fan Motor kW, Convert KW-Amp, Duct gauge/weight, Threaded rod hanger sizing, Velocity guide.
 Duct converter module to convert duct sizes between round, rectangular and oval duct.
 rhoAIR module to find air density and other pyschrometric air properties at state point. see rhoAIR page ...
 Louvre sizer module to size louvre opening required for structural opening.
 Fan Motor kW module to calculate electrical power consumption.
 Convert KW-Amp module to convert electrical KW - Amp, and calculate KVA.
 Duct gauge/weight module to find duct weight, perimeter and surface area for rectangular, round and oval duct with built-in duct gauge selections (Standard (uncoated) Steel, Galvanized steel, Stainless steel and Aluminium duct).
 Threaded rod sizer module to size and select threaded hanger rod with built-in metric-english series of rod sizes, tensile stress calculator and maximum load calculator. see 
tRod page ...

 Velocity guide Module to provide recommended duct velocity for main and branch duct.

 SI & IP units setting
 Save results function.



Note: Ductulator+ does not calculate fitting / dynamic loss.


. . . & lots more than just a conventional ductulator  

Unlike the conventional hand-held ductulator which is built for round duct sizing with equivalent rectangular duct sizes, velocity  & friction loss rate for round duct, pre-calculated for the duct roughness of 0.09mm and limited duct sizes, Ductulator+ offers you the flexibility in duct sizing for various duct shapes and different materials such as concrete duct, flexible duct, etc.


Ductulator+ is designed to offer you the greatest flexibility in duct sizing:
- options for Equal Friction method, Velocity method, by Duct Dimensions or find Airflow.

- options for round or rectangular or oval duct shape.
- use Colebrook equation in solving friction factor.
- use hydraulic diameter (not equivalent diameter of round duct) for rectangular and oval duct sizing.

- duct converter for round, rectangular & oval duct.


Ductulator+ gives you detail results like Flow area, Hydraulic diameter, Reynolds number, Friction factor and Velocity pressure, if you need it and save the results.


It has built-in tools like Duct Velocity Guide, Louvre Sizer, Duct Gauge and Weight calculator, Psychrometric air properties calculator and Fan Motor kW, Convert kW-Amp, Threaded rod sizer. Pictures explain everything -  view Ductulator+ explained. 


 Duct Sizing Methods  

Ductulator Plus offers 3 commonly used methods of duct sizing:

1) The traditional Equal Friction Method of duct sizing is often preferred as it is easy to use and less time-consuming. This method uses a constant pressure loss per unit of duct length. Generally, 0.8 Pa/m (0.1 in.wc/100 ft) of constant pressure loss per meter run has been widely practised in duct sizing.

Because there are practically unlimited number of duct sizes for a given design air flow, the duct sizing problem is solved by iteration technique. Click "calculation explained" for detail.

2) Velocity method is often used when acoustic requirements or minimum air transport/duct velocity is given. 


3) by Duct Dimensions method is generally used to find duct friction loss rate for an existing "as-built" duct. 


4) find Airflow method comes handy when you need to know how much airflow for a given existing or new duct sizes. 


The formula used in duct sizing is based on the ASHRAE Fundamentals.





 Units in Ductulator+  


Both SI & IP units are available in Ductulator Plus.


Parameter SI Units  IP Units
 Friction loss ratePa/m in.wc/100 ft 
 Duct roughness mmft 
 Air Volume





 Duct dimension mm in.
 Duct velocity m/s FPM
 Flow areamft
 Hydraulic diameter mm in.
 Velocity pressure Pa in.wg

 Did you know? . . . (1) Equivalent cross-sectional Area!  


If you want the same duct friction loss rate, it is inappropriate to convert duct size based on equal cross-sectional area, be it from round to rectangular or square to rectangular. This is because rectangular duct is less efficient than round duct; rectangular duct is less efficient than square duct. See example below, the flow areas (ie, cross-sectional areas) are diffierent for the same duct frictional loss rate.


 Did you know? . . . (2) Hydraulic diameter vs Equivalent diameter!  


For duct with shapes that are not round, hydraulic diameter does not equal to equivalent diameter. For circular duct, hydraulic diameter is the same as the diameter of a round duct.


For any duct shapes, hydraulic diameter = 4 x cross-sectional area / perimeter. Ductulator Plus uses this approach to find duct sizes.


For rectangular duct, equivalent diameter = 1.30 x {(Width x Height)0.625 / (Width + Height)0.25}. 


For oval duct, equivalent diameter = 1.55 x (cross-sectional area)0.625 / (perimeter)0.25.


 Example: Duct Sizing at job site (in SI units)  


An existing duct 600mm (W) x 500mm (H) carrying an airflow of 8000 CMH needs to be flattened to 300mm (H) to achieve the desired ceiling height.
Find the new duct size based on the existing duct friction loss rate.



Step 1: Find duct friction loss rate for the existing duct.

Step 2: Calculate new duct size with the given height constraint.


The following results are computed by the Ductulator Plus:


 Step 1 results

 Step 2 results

Duct Friction Loss Rate calculations


Retangular Duct sizing......
Duct height =500 mm
Duct width =600 mm
Air volume =8000 CMH
Duct roughness=0.09 mm
Duct velocity =7.41 m/s
Friction loss rate=0.9781 Pa/m

(1) Flow area, A = 0.300 sq.m
(2) Hydraulic dia, Dh = 545.5 mm
(3) Reynolds nos, Re = 268,283
(4) Relative roughness, e/Dh = 0.000165
(5) Friction factor, ff = 0.016205

(6) Velocity pressure, Pv = 33.03 Pa
(friction factor solved by ColeBrook equation)

Equal Friction Method calculations


Retangular Duct sizing......
Friction loss rate =0.9781 Pa/m
Duct roughness, e =0.09 mm
Air volume =8000 CMH
Duct height =300 mm
Duct width =1100 mm

Duct velocity =6.74 m/s


(1) Flow area, A = 0.330 sq.m
(2) Hydraulic dia, Dh = 471.2 mm
(3) Reynolds nos, Re = 210,908
(4) Relative roughness, e/Dh = 0.000191
(5) Friction factor, ff = 0.016916

(6) Velocity pressure, Pv = 27.34 Pa
(friction factor solved by ColeBrook equation)

 Note: For air balancing by Proportional Method, see  AirTAB superEZ.



Experience yourself the power of Ductulator plus+

Price: USD 14.90 



Download now:

product detail 


OS requirements: Windows PC.


For Android OS, see                            


Accept: credit card payment with PayPal 


1) Pay & instant Download via Click2Sell service:



Note: check your email /junk mail after making payment.

in SI & IP units






 view Ductulator+ explained




 Duct Material Selections



 Tools Menu



Duct Converter



Louvre Sizer



 Duct Gauge & Weight Calculator




Fan Motor kW



kW-Amp Converter



Psychrometric Air Properties calculator (rhoAIR)


Threaded Rod Sizer (tRod)