Fan Design Calculator v1

Price: £38.12 (£38.12 Inc. VAT)
Fan design calculator


Whilst most fan designs (axial, Sirocco, centrifugal, etc.) are suitable for many applications including; extraction, distribution, compression, etc. and their performance is almost entirely governed by blade design and rotational speed, flow and head characteristics are generally governed by the fan's inlet and/or outlet ducts.

Most technical reference books and related data sites make this subject a little more complicated than it needs to be. CalQlata has tried to simplify the subject with the fan calculator and its technical help page on this website.


go to the technical help page
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You calculate the performance characteristics of the blade using either the Axial or Centrifugal calculation option; the output data from which you use to calculate the performance of the fan.


The performance of a generic fan is based upon volumetric flow rate and blade efficiency (both of which can be determined using the Axial and Centrifugal calculation options), the outlet area of the fan diffuser and the inlet and outlet atmospheric conditions.

The generic calculation option therefore defines the performance characteristics of the fan using calculation results from Axial or Centrifugal.

Axial & Centrifugal (fan-blade design)

Whilst these calculation options are primarily for the performance characteristics of an impeller (via blade configuration), they also offer the performance effects of an external casing.

Their output data can be used for input in the Generic calculation option.

Fans provides the most efficient blade inlet angle (minimum inlet loss) should you wish to use it. You alter the outlet angle manually in order to minimise the outlet loss and thereby maximise impeller efficiency.

Fans also provides lists of various output data (against rising impeller speed) for plotting in your preferred spreadsheet.


For help using this calculator see Technical Help

Fans Calculator - Options


... calculates the performance characteristics of a generic fan with regard to the change in properties and behaviour of the air from inlet conditions to outlet

You enter: and the Fans calculator will provide:
  • Volume flow rate
  • Inlet pressure
  • Outlet pressure
  • Temperature
  • Relative atomic mass
  • Outlet area
  • Source volume
  • Efficiency
  • Universal gas constant
  • Gravitational acceleration
  • Fan power
  • Mass flow rate
  • Mole flow rate
  • Velocity
  • Inlet density
  • Outlet density
  • Velocity pressure
  • Discharge pressure
  • Static pressure
  • Pressure head
  • Rate of change of the ‘Source volume’

AXIAL (Blade Design)

... calculates the performance characteristics of your axial fan based upon its blade configuration and rotational speed

CENTRIFUGAL (Blade Design)

... calculates the performance characteristics of your centrifugal fan based upon its blade configuration and rotational speed

... both of which utilise the same input and output data as follows:

You enter: and the Fans calculator will provide:
  • Impeller speed
  • Blade inlet angle
  • Blade outlet angle
  • Impeller inside diameter
  • Impeller outside diameter
  • Impeller width
  • Inlet air density
  • Inlet air pressure
  • Inlet air temperature
  • Gravitational acceleration
  • Specific gas constant
  • Frictional resistance (air)
  • Ratio of specific heats
  • Number of blades in the impeller
  • Casing outlet area
  • Volume flow rate
  • Torque required to drive air
  • Power required to drive air
  • Pressure increase across impeller
  • Air density at impeller outlet
  • Head generated (before losses)
  • Inlet shock loss (head)
  • Frictional loss (head)
  • Outlet loss (head)
  • Head (after losses)
  • Head loss efficiency
  • Alternative head loss efficiency
  • Isentropic efficiency
  • Absolute inlet velocity
  • Absolute outlet velocity
  • Axial inlet velocity
  • Axial outlet velocity
  • Impeller inlet velocity
  • Impeller outlet velocity
  • Inlet velocity over blade
  • Outlet velocity over blade
  • Inlet rotational velocity
  • Outlet rotational velocity
  • Impeller outlet and inlet areas
  • Pressure inside casing outlet
  • Air-velocity inside casing outlet
  • Air-density inside casing outlet
  • Head at casing outlet
  • Power consumption due to casing

Note: Fans is a universal calculation tool. For final design purposes, CalQlata would recommend that you use the specification and procedures issued by your supplier for the selected product.

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