9.0" round duct

Nominal size: 10"

Cross-section: 64.0 sq in

Equivalent rectangular: 8" x 13" (approx)

Typical: 600-900 FPM for branch ducts, 700-1200 FPM for main ducts.

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About Duct Size

Duct Size solves a specific problem that comes up daily for anyone dealing with this task: doing it once, fast, without an account. Everything happens client-side, which means your files and data never leave your machine. The interface is intentionally minimal so you can focus on the task instead of learning the tool. It is one of about a hundred utility tools that share the same philosophy: do one thing, do it well, get out of your way.

When you'd reach for Duct Size

  • You're on a public or shared machine and don't want to leave traces of what you're working on.

    Travelers, contractors, anyone working from a friend's computer.

    Nothing is uploaded, nothing persists if you're not signed in.

  • You need to handle a one-off task right before a meeting and don't have time to install anything.

    Anyone working remotely on a borrowed or restricted machine.

    Open the page, get the result, paste it into your doc — under a minute.

  • You're hitting the daily limit of a paid SaaS and need a backup option for a single quick job.

    Marketers and ops people whose primary tool is metered.

    Stay productive without burning credits.

  • You're cleaning up a folder of files that accumulated over a project and need to standardize them.

    Designers, writers, and developers wrapping up deliverables.

    Drop each file in, copy the output, move on.

Frequently asked about Duct Size

Are my files uploaded to a server when I use Duct Size?
Duct Size processes everything in your browser using local APIs. Your files never leave your device.
Do I need to create an account to use Duct Size?
No. Duct Size works without any signup. We only ask for an email if you decide to subscribe to a paid plan.
Is Duct Size really free?
Yes — Duct Size is free for unlimited personal use, with no account required and no watermark on the output.
What browsers does Duct Size support?
Every modern browser released in the last three years: Chrome, Firefox, Safari, Edge, Brave, Opera.
Will Duct Size change my original file?
Never. Duct Size only reads your input file and produces a new output file.

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