Duct Calculator Elite1.5.1

Duct Calculator Elite(TM) replaces your ductulator wheel with fast, precise duct sizing built on the friction-loss equations of the ASHRAE Handbook - Fundamentals. Trusted by HVAC professionals, mechanical engineers, and contractors since 2013. One price - no subscriptions, no ads, no accounts.

THREE CALCULATORS, ONE TAP APART
. DUCT SIZE BY AIRFLOW - Set airflow and either velocity or friction, and solve for round and rectangular duct dimensions. Specify the rectangular aspect ratio to match your available space. The nearest standard round and rectangular sizes are shown with the friction they actually run at.
. DUCT SIZE BY DIMENSION - Enter a round diameter or rectangular height and width, then lock airflow, velocity, or friction and solve for the remaining variables.
. PRESSURE DROP - Convert between duct length, pressure drop, and friction. Find the exact pressure drop of a given installation, or the maximum duct length that maintains your design pressure drop.

DESIGN TOOLS
. FRICTION RATE - Enter your available static pressure and duct run, add fittings from a built-in list of typical equivalent lengths (elbows, tees, wyes, supply boots), and get your total effective length and target friction rate - the Manual D style residential design workflow. Then send the result straight into Duct Size by Airflow with one tap.
. AIRFLOW FROM HEAT LOAD - Enter a sensible heat load and temperature difference to get the required airflow, corrected for air density.

ENGINEERING-GRADE MATH
Solves the Colebrook friction-factor equation directly for each duct material's surface roughness - the same method behind the ASHRAE friction chart - rather than interpolating from lookup tables. Roughness values come from Table 1 of the 2025 ASHRAE Handbook - Fundamentals, and the app shows you the one it used. Rectangular results use the Huebscher equivalent-diameter equation; air density is corrected for your temperature and elevation, and air viscosity for your temperature, so results hold up at altitude and outside room temperature. Below the turbulent range where the published methods agree, results are flagged as approximate.

PRECISE ENTRY, BUILT FOR THE FIELD
Type exact values directly in place - no cumbersome sliders, no pop-up entry screens. Confirm with a tap and every dependent value recalculates instantly. A clean layout keeps every result in view as you work, and everything runs fully offline.

CONFIGURED FOR REAL JOB CONDITIONS
. Duct dimensions: inches, centimeters, or millimeters
. Airflow: CFM, cubic feet per second, cubic meters per second, cubic meters per hour, or liters per second
. Velocity: feet per second, feet per minute, or meters per second
. Pressure loss: inches of water per 100 ft or pascals per meter
. Duct materials: galvanized steel, spiral steel, galvanized spiral (corrugated), aluminum, uncoated carbon steel, PVC plastic pipe, concrete, phenolic duct (pre-insulated), flexible duct (metallic), flexible duct (helix core, insulated), fibrous glass liner (spray coated), and fibrous glass liner (faced, smooth)
. Air temperature (°F, °C, K) and elevation (feet or meters) corrections

The next time you head to a meeting or out to the job site, leave the ductulator at home - everything you need is on your iPhone or iPad.

Questions or ideas for the next version? Email techsupport@cyberprodigy.com - we read every message.

Version History Added three more duct materials to the list, plus airflow in m³/h and the ASHRAE roughness value behind every material. The air temperature and elevation adjustment covers viscosity as well as density.

NEW
• Three more duct materials: phenolic (pre-insulated), galvanized spiral (corrugated), and flexible duct with an insulated helix core. The two fibrous glass liners now use ASHRAE's names.
• Airflow in cubic meters per hour (m³/h).
• Preferences shows the absolute roughness used for every material, from Table 1 of the 2025 ASHRAE Handbook — Fundamentals. Tap ⓘ where ASHRAE gives a range rather than a single number.
• A flag on results where flow leaves the turbulent range and the published friction methods stop agreeing.

NON-STANDARD AIR
Sizing has always adjusted for your air temperature and elevation; this version lets air viscosity vary with your temperature too, as the ASHRAE Handbook prescribes for air outside the chart's range. Near sea level at ordinary temperatures nothing changes; higher or hotter, rates read 3–13% higher than in previous versions, the top of that range only where extreme heat and altitude combine. Your saved air temperature and elevation carry over unchanged; new installs now default the air temperature to 70 °F and the elevation to sea level.

FIXED
• A unit switch now re-checks the converted value against the new unit's range.
• Pressure Drop accepts metric duct length up to 150 m. 1.5.1 Sep 2 • NEW Design tab: calculate your target friction rate from available static pressure, duct length, and fittings (Manual D style), then send it straight into Duct Size by Airflow
• NEW Airflow from Heat Load: enter a sensible load and temperature difference to get density-corrected airflow
• Redesigned interface with a cleaner, card-based layout
• New inline value entry — edit any field in place and confirm with a tap
• Lock friction in Duct Size by Dimension and solve for airflow and velocity
• Localization improvements across all supported languages, plus compatibility updates for the latest iOS 1.5.0 Jul 12 -Overall performance and compatibility improvements for the latest iOS platforms. 1.4.1 10/01/2024 -Overall performance and compatibility improvements for the latest iOS platforms.
-Added ability to lock friction on "Duct Size by Dimension" calculator and solve for airflow and velocity. 1.4.0 10/17/2022 -Performance and compatibility improvements for latest iOS platforms and devices.
-Resolved bug from user feedback. 1.3.3 01/11/2021 -Overall performance and compatibility improvements for latest iOS platforms. 1.3.2 06/29/2020 -Overall performance and compatibility improvements for latest iOS platforms. 1.3.1 05/19/2019 -Overall performance and compatibility improvements for latest iOS platforms. 1.3 06/01/2017 -Added support for iOS 8
-New calculator for duct length/pressure drop conversion 1.2 12/29/2014 -Added support for iOS 7 1.1.1 09/27/2013 -Added language support for German, Spanish, French, Japanese, Korean, Portuguese, and Simplified Chinese
-Added landscape view on iPad 1.1 07/10/2013 1.0 07/01/2013