Duct Velocity Calculator

The Duct Velocity Calculator is built for HVAC airflow checks for round and rectangular duct sections. It supports round and rectangular duct area calculations, then divides airflow by area.

The calculator selects the duct area formula from the chosen shape and divides airflow by that area.

• Check HVAC duct sizing.
• Compare round and rectangular duct sections.
• Convert airflow into air speed.

Duct velocity uses the same continuity formula: v = Q / A

Use the formula panel beside the calculator to keep the variables visible while you enter values.

• Q = airflow
• A = duct cross-sectional area
• round A = pi*d^2/4
• rectangular A = width*height

Enter airflow, duct shape, and the matching duct dimensions. The calculator keeps the fields focused on this specific problem so you do not have to adapt a generic velocity form by hand.

After you press Calculate, the result panel shows duct air velocity, duct area, and ft/min for HVAC comparison. Reset clears the example values so you can start a fresh scenario.

• Use consistent real-world measurements for the selected scenario.
• Check that time, area, mass, or temperature values are positive where the formula requires them.
• Read the step-by-step substitution before using the final number in homework, design notes, or planning.

An airflow of 0.8 m^3/s through a 0.4 m round duct has an average velocity of about 6.37 m/s.

Higher duct velocity can increase noise and pressure loss, while lower velocity may require larger ductwork.

The extra output rows give practical companion values so the answer is easier to compare against common units or planning targets.

The duct section is fully open, dimensions are internal dimensions, and airflow is steady.

For professional engineering, safety, aviation, ballistics, medical, or project-management decisions, treat the result as a calculation aid and verify it against the standards used in your field.