Duct Size Calculator
Duct Size Calculator — quick estimate
Get the round duct diameter and the equivalent rectangular duct size for a given airflow and velocity — the quick check every HVAC layout needs. Adjust the inputs, then get an engineered ductwork design.
Your airflow
Sizes ducts on the velocity method (area = airflow ÷ velocity). A full design also balances friction loss, noise (NC) and the static pressure across the run.
Get an engineered ductwork design — free
Our HVAC engineers will size the full duct network, diffusers and static pressure for your project. We'll attach the estimate above automatically.
Have a BOQ, drawing or tender for this scope? Send it for an item-wise rate-analysis review →
Your request is in
Thanks! Our HVAC team will send your tailored ductwork design within one business day.
Indicative estimates only — not a binding design. Actual ducting depends on the friction rate, aspect ratio, fittings, noise criteria and available ceiling space.
Got your number — what next?
A calculator gives you a first figure. These take it further.
The work itself
The terms behind it
Delivered work with this scope
- Electrical & Mechanical for a Global Manufacturer— client withheld
- Bespoke MEP for a Global Semiconductor Leader— NXP Semiconductors
Need an exact BOQ, rate analysis or measurement sheet?
This is a quick engineering estimate. For tendering, billing or audit, our QS & estimation team prepares an item-wise BOQ, rate analysis and a verified measurement sheet to IS / CPWD norms — backed by 15+ years and ISO 9001:2015 quality processes.