Stop guessing
duct sizes.
Size a round or rectangular duct from airflow in seconds — plus the friction rate, right from the job site. No account, no ads, no guesswork.
Built for the job site.
Every feature is designed for HVAC contractors and DIY installs who need a real number before they cut metal.
Round & Rectangular
Size from CFM and target velocity, both shapes, fully free. Friction rate included with every result.
Reverse Mode
Already have a duct size on hand? See exactly what airflow it can carry — built for service calls and retrofits.
Branch Calculator
Size a trunk and every branch run at once, with a warning if the numbers don't add up.
Every Duct Material
Galvanized, flex duct, PVC, and fiberboard — each with its own accurate friction rate.
Save by Job
Every sizing saved and grouped by job, ready to reopen or hand off to the next visit.
Fully Private
No account. No login. Your sizings and job data stay on your device — not on a server.
HVAC Ductulator Pro
Unlock reverse mode, the branch calculator, every duct material, and unlimited saved sizings. Start with a 3-day free trial on the weekly plan — no charge until the trial ends.
- Reverse mode — know what an existing duct can move
- Branch calculator for full trunk-and-branch runs
- Flex duct, PVC, and fiberboard, in addition to galvanized
- Unlimited saved sizings and PDF export, organized by job
Free to download.
Get the numbers you need before you cut metal.
Get HVAC Ductulator on the App StoreSupport
Email SupportEmail support@fosterapps.com and include:
- A short description of what you were doing.
- Steps to reproduce the issue, if you know them.
- What you expected to happen vs what actually happened.
- Your device model and iOS version.
- Any screenshots that might help.
Privacy policy
Read the full policy at the HVAC Ductulator privacy page.
Terms of use
Read the full terms at the HVAC Ductulator terms page.