Does it use a friction chart or an acoustic limit?

No. It applies the velocity method only. The design velocity is your criterion; no friction-rate chart, roughness or noise criterion is embedded.

How do I check the chosen size?

Run the free Duct Velocity Check with the size you finally select to confirm the actual velocity against your own limit.

Does it size the whole duct run?

It sizes one section at a time. Static pressure for the run is handled by the External Static Pressure tool.

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Duct Sizing

Determine air duct sizes.

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Duct sizing by the velocity method needs two inputs: the airflow and the design velocity you accept for that duct type and location. The calculator returns the required area, the equivalent round diameter and the rectangular width for the height you can fit in the ceiling void.

Method and assumptions

A(m²) = Q(m³/s) ÷ v(m/s)
D(round) = √(4A/π)
Width(rect) = A ÷ chosen height

The design velocity is a user-entered criterion based on the duct type and acceptable noise level for the project.
A preliminary decision-support estimate: the result does not replace an approved design calculation or review by a competent authority.
All percentages and inputs are user-defined; the calculation is purely arithmetic and assumes no particular code or specification.

Frequently asked questions

Does it use a friction chart or an acoustic limit?: No. It applies the velocity method only. The design velocity is your criterion; no friction-rate chart, roughness or noise criterion is embedded.
How do I check the chosen size?: Run the free Duct Velocity Check with the size you finally select to confirm the actual velocity against your own limit.
Does it size the whole duct run?: It sizes one section at a time. Static pressure for the run is handled by the External Static Pressure tool.

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