DuctRule: HVAC Duct Sizing
The ductulator, done right
$4.99 · Designed for iPad. Not verified for macOS.
The ductulator from your van, with Colebrook-White solved for every value instead of read off a curve. No signal, no account, nothing collected.
The ductulator in your van is two cardboard discs and a rivet. This is that tool,
on your phone, with the arithmetic done properly.
Turn the outer ring to the airflow you have. Turn the blue wheel to the friction
rate you are designing to. The answer sits in the middle, under the hairline:
round diameter, air velocity, and the next stock size up. Up, never down, because
a duct one size over costs a little sheet metal and a duct one size under costs
the job.
The velocity is not decoration. The ring around the answer runs green while the
air stays inside the range for the run you picked, and turns amber the moment it
leaves. Supply trunk, branch and return have different ranges, and you choose
which one you are sizing. A duct that is slightly too small is quiet on paper and
loud in the room.
Under the dial are the rectangular sizes of equal friction, each with the velocity
it produces, so you can trade depth for width when the ceiling is tight. Tap the
one you are going to cut. Flat oval is there too, and so is the other direction:
fix a height and the app solves the width.
Save a run under the name you would write on the duct itself, like supply trunk A
or branch to office 2, and the whole system becomes one list you can read back at
the desk or send to the office.
The friction comes from Colebrook-White, solved for every value rather than read
off a power-law fit, with the roughness of galvanised steel and standard air. That
is the same equation the printed chart was drawn from, which is why a printed chart
and this app can differ a little in the middle of the range. The difference is in
favour of the app, and the app says where its numbers come from.
It works with no signal because it never asks for one. Nothing to sign into,
nothing to subscribe to, no advertising, and nothing about you leaves the phone.
there is no network code in it at all.
Inches and CFM, or millimetres and litres per second. English, Spanish and
Portuguese. Light and dark, and the instrument is drawn for both.
Ratings & Reviews
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The developer, Charles Hasse, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Charles Hasse
- Size
- 2.4 MB
- Category
- Business
- Compatibility
Requires iOS 26.1 or later.
- iPhone
Requires iOS 26.1 or later. - iPad
Requires iPadOS 26.1 or later. - Mac
Requires macOS 26.1 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.1 or later.
- iPhone
- Languages
English and 2 more
- English, Portuguese, Spanish
- Age Rating
4+
- 4+
- Copyright
- © Vump
