HVAC Duct Sizer

About

HVAC Duct Sizer helps mechanical engineers, estimators and commissioning technicians size ductwork directly in the browser.

Paste a line such as 5500 cfm at 2000 fpm, read selected text, scan the visible page or decode clipboard content after an explicit click. The extension calculates required area, theoretical round diameter, commercial round sizes, actual velocity, rectangular equivalents and approximate friction loss.

It supports:
- CFM and FPM
- m3/h, m3/s and m/s
- round duct sizing
- nearest and velocity-safe commercial diameters
- rectangular equivalent suggestions
- Reynolds number and friction estimate
- batch calculations
- local CSV, JSON and text reports
- temporary page highlights

Privacy and safety:
- no account
- no server
- no API request
- no broad website permission
- no remote code
- no stored project data by default

Important: this tool is an estimating aid. It does not certify mechanical design, code compliance, acoustics, fire/smoke requirements, pressure class or manufacturer approval.