10 Inch Duct Calculator
What is the CFM for a 10 inch duct? Calculate airflow capacity, velocity limits, and rectangular equivalents for 10" HVAC ducts. Includes metal and flex duct notes.
Airflow Capacity for 10" Round Duct
A 10 inch round duct has a cross sectional area of 78.5 square inches (0.545 sq ft). The table below shows the CFM airflow at different air velocities.
| Velocity (FPM) | Airflow (CFM) | Noise Level | Use Case |
|---|---|---|---|
| 600 FPM | 327 CFM | ✅ Quiet | Residential supply |
| 700 FPM | 382 CFM | ✅ Quiet | Residential supply |
| 800 FPM | 436 CFM | ⚠️ Moderate | Commercial supply |
| 900 FPM | 491 CFM | 🔊 May be noisy | Industrial |
Technical Specifications
Rectangular Equivalent
14x8 or 12x10 inches
Based on ASHRAE equivalent diameter formulas.
Max Recommended CFM
491 CFM
Based on 900 FPM (max residential velocity).
10 Inch Metal vs. Flex Duct
While the nominal diameter is the same, 10" flexible duct has significantly higher air resistance than smooth 10" galvanized sheet metal duct.
- Metal Duct: Delivers approximately 382 CFM at 0.1 friction rate.
- Flex Duct: Usually requires a 1.5x resistance factor. To deliver the same airflow, you may need to increase to a 12" flex duct.
- Return Air: For a return duct, a 10" round duct is generally limited to 273 CFM to maintain quiet operation (600 FPM).
Frequently Asked Questions
How much CFM can a 10 inch duct handle?
A 10 inch round duct can handle between 273 and 491 CFM. For residential supply branches, it is typically used for 382 CFM at 0.08 friction rate.
What is the rectangular equivalent of 10" round?
The most common rectangular equivalents for a 10 inch round duct are 14x8 or 12x10 inches.
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