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Calculation Machine

Dust Collection CFM Calculator

Workshop dust collector sizing by machine.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Collector size needed
700 CFM
Duct velocity
4,840 FPM
Transport verdict
Higher than needed — upsize duct to cut static
Duct area
0.136 sq ft
Ideal duct diameter
5.5 in

Quick answer

Each machine has a port CFM requirement, and duct velocity must stay above 3,500–4,000 FPM to keep chips moving.

The formula

CFM = sum of active machine requirements; velocity = CFM / duct area

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Largest machine requirement600 CFM
  • Second machine (if run together)0 CFM
  • Main duct diameter5 in
  • Duct leakage allowance10 %

Result

  • Collector size needed700 CFM
  • Duct velocity4,840 FPM
  • Transport verdictHigher than needed — upsize duct to cut static
  • Duct area0.136 sq ft
  • Ideal duct diameter5.5 in

How to use the Dust Collection CFM Calculator

  1. 1Enter the CFM demand of the biggest machine you run.
  2. 2Add a second machine only if you genuinely run two at once.
  3. 3Check that duct velocity stays between 3,500 and 4,500 FPM.

Frequently asked questions

Why is velocity so critical?

Below about 3,500 FPM heavy chips drop out of the airstream and block the duct.

Is a shop vac enough?

A shop vac gives high suction but only 60–150 CFM — fine for sanders, useless for a table saw.

About this calculator