Printable Duct Size Equivalent Chart
This sheet is for HVAC installers, duct designers, and anyone comparing rectangular duct to round duct sizes. It lists rectangular equivalents in a simple table with columns for size, equivalent round, CFM at 0.08, and CFM at 0.10. Example rows include 6 × 4 in, 8 × 4 in, and 10 × 4 in, along with their round equivalents and airflow values. The chart uses Huebscher equivalent diameter.
Free printable · PDF
- 1 page
- US Letter — choose “Fit to page” for A4
- PDF, 62 KB
Free for personal, family and classroom use.
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Use it to match a rectangular duct to a nearby round size, then check the airflow values for the two pressure drop columns. It is set up as a one-page Letter PDF, so it works well as a quick reference at the jobsite, in the office, or during layout checks.
Good for
- Compare rectangular and round duct sizes
- Check airflow at 0.08 and 0.10
- Confirm equivalent diameter during layout
Tip: Print it at full size and keep it with your duct sizing notes.
4 files · PDF, XLSX, DOCX
Get every sheet: Duct Sizing Reference Pack
This sheet plus 3 more in one download, with the editable Excel and Word files. Printable round duct CFM chart at five friction rates, rectangular equivalents table, an Excel duct sizing calculator and a room-by-room airflow worksheet.
$3.00 USD, one-time 4 files · about $0.75 each
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