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Calculation Machine

Restaurant Exhaust CFM Calculator

Commercial kitchen hood exhaust airflow.

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

Your values

ⓘ Live results

Results
Exhaust airflow
3,000 CFM
Rate
300 CFM per linear foot
Makeup air (80%)
2,400 CFM
Duct area at 1800 FPM
1.67 sq ft
Fan static allowance
1.0 - 1.5 in wc typical

Quick answer

Commercial hood exhaust is sized in CFM per linear foot of hood, rising with appliance duty from light to extra heavy.

The formula

CFM = hood length x CFM per linear foot

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Hood length10 ft
  • Hood typeWall-mounted canopy
  • Appliance dutyMedium (fryers, ranges)

Result

  • Exhaust airflow3,000 CFM
  • Rate300 CFM per linear foot
  • Makeup air (80%)2,400 CFM
  • Duct area at 1800 FPM1.67 sq ft
  • Fan static allowance1.0 - 1.5 in wc typical

How to use the Restaurant Exhaust CFM Calculator

  1. 1Measure the hood length and identify the heaviest appliance under it.
  2. 2Choose the hood style — island hoods need substantially more air.
  3. 3Provide 80-90% of the exhaust as tempered makeup air.

Frequently asked questions

Why is island so much higher?

There are no side walls to contain the plume, so cross drafts pull effluent out.

Can I undersize to save energy?

No — undersized hoods spill grease-laden vapour into the kitchen and fail inspection.

About this calculator