HVAC Sizer

For iPhone and iPad

Duct, pipe and condensate sizing in seconds.

Enter the airflow, GPM or lb/h and the right size appears instantly, checked against your friction and velocity limits. Then build a schedule and export it to Excel.

Coming soon to the App Store

  • No account
  • No ads
  • Works offline
  • IP and SI units
HVAC Sizer sizing a 2,400 cfm rectangular duct to 22 by 16 inches

Features

An answer in seconds, not a spreadsheet.

Built by a mechanical engineer for engineers, designers and contractors who size duct and pipe every day.

Ductwork

Round, rectangular and flat oval

  • One-tap presets for LP supply, MP supply and return/exhaust
  • Options within your maximum aspect ratio, with the least-sheet-metal size marked
  • Lock a depth for tight ceiling space and the app solves the other dimension
  • Darcy-Weisbach with Colebrook, corrected for altitude and air temperature

Piping

Any pipe, any fluid

  • Hydronic: water, ethylene or propylene glycol from 0 to 100%
  • Domestic hot and cold water, friction in psi per 100 ft
  • Saturated steam from vacuum to 600 psig
  • Steel, copper, PEX, PVC, CPVC and HDPE with true inside diameters

Condensate

Condensate, sorted

  • Two-phase returns sized on flash steam at return pressure
  • Flash fraction, flash steam and liquid flow shown
  • Gravity liquid lines sized with Manning’s equation for your slope and depth of flow

Results

See the margin, not just the size

Every result shows how close it is to each limit in green, amber or red, and whether friction or velocity governs. Nearby sizes are listed so you can step up or down with one tap.

Schedule

Batch size, then export

  • Add any result with a tag like S-1 or P-12; tags count up automatically
  • A separate schedule for each project, with notes on any row
  • Export a CSV, or copy and paste straight into Excel

Settings

Your standards, saved

Friction and velocity limits, materials, glycol mix, fluid temperatures, aspect ratio, steam pressure split and condensate slope: set them once and they’re saved on your device. Switch between IP and SI at any time.

Screenshots

See it in action

Pipe sizing: hydronic, domestic and steam, with glycol mix and temperature
Condensate sizing: a two-phase return sized on flash steam
A tagged sizing schedule with Copy for Excel and Export CSV
Settings: IP or SI units and default friction and velocity limits
Duct sizing in dark mode
iPad layout with inputs and results side by side

Made for speed, on site or in the office.

Every screen size

iPhone, iPad and iPhone Duo, folded or unfolded, with inputs and results side by side on larger screens.

Fast entry

A number pad on every field, and tapping a field selects its value so you can just type. Light and dark mode.

Private by design

No account, no ads, no tracking and no internet connection needed. Your projects stay on your device. Read the privacy policy.

The developer

Built by an engineer

HVAC Sizer is designed and developed by a mechanical engineer. It uses the same methods engineers check by hand: Darcy-Weisbach with Colebrook, Huebscher and ASHRAE equivalent diameters, and IAPWS-IF97 steam and water properties.

Questions, bug reports and feature ideas are welcome on the support page.

Results are engineering estimates based on standard methods and published fluid properties. Always verify final designs against applicable codes, standards and manufacturer data.