Skip to main content
duct cfm calculator AC airflow

How Much Airflow Does My AC Need?

A technical airflow triage tool for ducts, returns, and filters. It uses Florida humid-climate CFM-per-ton ranges and flags undersized returns.

Direct answer

Many Florida AC systems target about 350-400 CFM per ton, with humid-climate setups often using the lower end for moisture removal.

Why this matters

Use this when a new system quote ignores ducts, static pressure, returns, or filter size.

The public-safe rule

This page gives an educational planning result. Final quote, rebate, payment, package, and installer details wait until the customer and home record are saved inside the assessment flow.

Start exact assessment
Live calculator

Run the numbers.

Calculator inputs

Tune the estimate

Live result

1,050 CFM target airflow

3 tons at 350 CFM per ton gives a 1,050 CFM target.

Target airflow

1,050 CFM

CFM per ton

350

Filter velocity

378 FPM

Filter status

Filter face velocity is high

Florida humidity-control setups often use the lower end of the common airflow range, but final airflow must match manufacturer data and Manual D.

Ask the contractor to measure static pressure and delivered airflow after installation.

If filter velocity is high, discuss a larger return/filter cabinet or additional return path.

This is a planning estimate, not a final quote or engineering report. Field conditions, permits, equipment selection, ducts, electrical work, and installer verification can change the result.

Sources and assumptions

How this estimate is grounded.

The visible result, assumptions, and schema match. Structured data does not claim anything that is not also shown on the page.

Common questions

Short answers for homeowners.

Is 400 CFM per ton always right?

No. DOE Building America notes 350-400 CFM per ton is common, and 350 CFM per ton can support moisture removal in humid climates.

Why does filter size matter?

A small filter face area can raise filter velocity and pressure drop, which can reduce airflow and hurt comfort, capacity, and equipment life.

A calculator can narrow the decision. A saved assessment can price the real home.