Duct Calculator Elite

Duct Calculator Elite™ 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.
• 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. Rectangular results use the Huebscher equivalent-diameter equation, with air density corrected for your temperature and elevation.

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, redesigned interface keeps results on screen 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, 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: galv