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DUCT me – Duct Sizing
House size
sq ft
System size
Job name & advanced settings ›
Job name / address
Sq ft per ton
400 · hot / glass
500 · average
550 · PA / NJ
600 · tight house
700 · very efficient
CFM per ton
350
400
450
Friction (in/100 ft)
0.06
0.07
0.08
0.09
0.10
Return velocity
600 fpm · quiet
700 fpm
Trunk max fpm
700
800
900
Branch max fpm
600
700
800
900
Rooms
· splits airflow by sq ft
+ Add room
⚡ Quick fill
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Duct capacity chart
Size any duct
Airflow (CFM)
Duct type
Branch
Trunk
Return
Round ⇄ rectangle converter
Round diameter (in)
Or rectangle W × H
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