# Duct Area and Diameter Screening Calculator — United States

> Calculate an equal-area duct geometry for a specified airflow and velocity, not a fan-pressure design. USD planning view; stated limitations apply.

Page: https://askcalculators.com/us/duct-sizing/
Definition: https://askcalculators.com/us/duct-sizing/definition.json
JSON Schema: https://askcalculators.com/us/duct-sizing/schema.json
Version: 20.16.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/us/duct-sizing/?unitSystem=imperial&airflow=423.7760006578631&velocity=13.123359580052492&rectangularAspect=2&unitRate=0&laborCost=0&deliveryCost=0&otherCost=0&costMultiplier=1&spreadPercent=15&taxRate=0

## Inputs
- unitSystem: Measurement system; type=select; optional; default=imperial; values=imperial|metric
- airflow: Required airflow; type=number; required; default=423.7760006578631; min=0; max=2118880003289.3154
- velocity: Specified duct air velocity; type=number; required; default=13.123359580052492; min=0.03280839895013123; max=3280839895013.123
- rectangularAspect: Rectangular width / height ratio; type=number; required; default=2; min=0.1; max=10
- unitRate: Material price per quoted duct project; type=money; required; default=0; min=0; max=1000000000000
- laborCost: Total labor allowance; type=money; required; default=0; min=0; max=1000000000000
- deliveryCost: Delivery allowance; type=money; required; default=0; min=0; max=1000000000000
- otherCost: Other fixed costs; type=money; required; default=0; min=0; max=1000000000000
- costMultiplier: Material/labor multiplier; type=number; required; default=1; min=0.1; max=10
- spreadPercent: Low/high sensitivity around the entered total; type=percent; required; default=15; min=0; max=100
- taxRate: Explicit tax allowance; type=percent; required; default=0; min=0; max=100

## Outputs
- area: Required clear cross-sectional area; format=number
- diameter: Equal-area round diameter; format=number
- width: Rectangular inside width; format=number
- height: Rectangular inside height; format=number
- materialCost: Material cost; format=currency
- laborCost: Labor allowance; format=currency
- deliveryCost: Delivery allowance; format=currency
- otherCost: Other specified costs; format=currency
- tax: Entered tax allowance; format=currency
- low: Low cost scenario; format=currency
- mid: Middle cost scenario; format=currency; primary
- high: High cost scenario; format=currency

## Formula
clear area = airflow ÷ velocity; equal-area round diameter = √(4A/π).

Inputs are converted to canonical units before evaluating this stated formula.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.

Notice: Illustrative defaults are not local quotes or verified legal rules. Dated reference components and user-entered assumptions are explicitly distinguished. Professional review is pending.