DuctPro: Duct Size Calculator

Replaces your duct wheel — and does what it never could.
DuctPro sizes ductwork the way you actually work: type the CFM, set your friction rate or velocity limit, and get the size instantly. Round, rectangular, flex (with compression correction), and flat-oval. Then do what no wheel can: build the whole job, watch external static pressure add up run by run, and export a clean duct schedule PDF for the file or the customer.

BUILT FOR THE FIELD
• Instant sizing by friction rate or velocity — results update as you type
• Round, rectangular (lock a side), flex with compression %, and flat-oval
• Reverse mode: pick a size, see what it carries
• Per-job static pressure tally with a fitting equivalent-length library
• Client-ready PDF duct schedule with your company name
• Velocity warnings when a run gets loud
• Imperial and metric. Works offline. No account.

HONEST ENGINEERING
Darcy–Weisbach and Colebrook–White, computed — not looked up. The methodology page shows every formula and assumption. No ASHRAE tables are reproduced.

SIMPLE PRICE
Round-duct sizing is free forever. One $9.99 purchase unlocks every duct type, reverse mode, jobs, and PDF schedules. That's it — no subscription, versus $33 for the plastic wheel in your truck.

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