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Calculation Machine

Air Compressor CFM Calculator

Compressor size from tool air demand.

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

Your values

ⓘ Live results

Results
Average demand
6.1 SCFM
With 30% margin
7.93 SCFM
Peak if all run together
21 SCFM
Approx motor size
2 HP
Tank suggestion
32 gallons

Quick answer

Compressor sizing adds each tool's CFM demand multiplied by its duty cycle, then adds a safety margin.

The formula

required SCFM = sum(tool CFM x duty) x 1.3

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Tool 1 demand5 CFM
  • Tool 1 duty50 %
  • Tool 2 demand4 CFM
  • Tool 2 duty30 %
  • Tool 3 demand12 CFM
  • Tool 3 duty20 %

Result

  • Average demand6.1 SCFM
  • With 30% margin7.93 SCFM
  • Peak if all run together21 SCFM
  • Approx motor size2 HP
  • Tank suggestion32 gallons

How to use the Air Compressor CFM Calculator

  1. 1List each tool's CFM at its rated pressure from the manual.
  2. 2Estimate how much of each minute the tool actually runs.
  3. 3Add 30% headroom so the compressor is not running continuously.

Frequently asked questions

Why does duty cycle matter?

A sander rated at 12 CFM used a fifth of the time only averages 2.4 CFM.

Tank size?

A bigger tank smooths peaks but does not increase sustained output.

About this calculator