HVAC Ductwork Calculator
Use our free HVAC Ductwork Calculator to quickly estimate duct size and airflow, based on key inputs like CFM, air velocity, and friction loss. Perfect for HVAC contractors, engineers, and builders.
HVAC Ductwork Formula
Correct duct sizing ensures proper airflow, energy efficiency, and comfort. Oversized ducts waste money, while undersized ducts create noise and inefficiency.
How this HVAC ductwork calculator works
This calculator uses airflow (CFM), velocity, and friction loss inputs to determine duct dimensions. It applies standard ASHRAE and SMACNA formulas to ensure safe, code-compliant duct sizing for residential and commercial HVAC systems.
When to use this HVAC ductwork calculator
Designing new ductwork layouts for residential or commercial projects
Verifying airflow balance in existing systems
Estimating material needs for duct installation
Comparing round vs. rectangular duct dimensions
Planning energy-efficient HVAC system designs
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Average Profit Margins by Industry
Understand how HVAC ductwork compares to other service industries. Below are typical net margin ranges:
HVAC Contractors
Ductwork Fabricators
Electrical Contractors
Plumbing Contractors
Roofing Contractors
Cleaning Services
Lawn Care
General Construction/Contracting
These benchmarks help HVAC professionals assess whether ductwork project costs are competitive and profitable.
Frequently Asked Questions
It provides reliable estimates using industry formulas. Always verify final designs with ASHRAE/SMACNA standards.
Airflow (CFM), velocity limits, duct shape, and friction loss.
Yes—results are provided for both shapes.
Absolutely. It works for homes, offices, and large buildings.
Indirectly via velocity and friction loss inputs. For precise analysis, use a duct design program.
Yes—larger ducts lower velocity and reduce noise but increase cost.
No—it only calculates duct dimensions. Pair with a cost calculator for full estimates.
Pair it with ServiceAgent.ai to generate automated ductwork layouts, estimates, and project reports.