How do you calculate paint booth airflow?

Multiply the booth opening area by the target face velocity, then multiply by fan and filter efficiency. A 96 ft2 opening at 100 ft/min and 90 percent efficiency gives 8,640 CFM.

What face velocity does a spray booth need?

Most codes and OSHA guidance call for about 100 ft/min average face velocity at the opening for open-face and crossdraft booths, higher for some operations.

Why is my actual CFM lower than the fan rating?

Loaded intake and exhaust filters, ductwork resistance, and fan wear all cut delivered airflow. The efficiency term in this calculator captures that derating.

How much airflow do dirty filters cost me?

At 90 percent efficiency in the example, you lose 960 CFM off a 9,600 CFM base. As filters load further, that loss grows and face velocity drops below spec.

How do I find booth opening area?

Multiply the width by the height of the working opening in feet. For a downdraft booth use the floor grate area over which air is pulled.

What happens if face velocity is too low?

Overspray escapes the capture zone, solvent vapor can approach the LEL, and finish quality suffers from dirt and dry spray. Below spec velocity is a safety and quality problem.

Finishing calculator

Paint Booth Airflow Calculator

Paint Booth Airflow computes the effective air volume, in CFM, that a spray booth actually moves through its opening after accounting for fan and filter losses. Finishing engineers and EHS staff use it to confirm a booth holds the code-required face velocity, typically around 100 ft/min, to capture overspray and stay under the LEL. Loaded filters and undersized fans quietly cut real airflow below the nameplate rating. This calculator multiplies opening area by target face velocity and derates the result by your fan and filter efficiency.

What this calculator does

Estimate paint booth exhaust airflow from booth opening size and target face velocity.
Use for booth ventilation checks, filter loading discussions, and maintenance planning.
It computes effective booth airflow as opening area times target face velocity times fan and filter efficiency, and shows the loss to inefficiency.

Formula used

Effective booth airflow = booth opening area × target face velocity × fan and filter efficiency

Inputs explained

Booth opening face area:
Target face velocity:
Fan and filter efficiency:

How to use the result

Use it during booth commissioning or filter maintenance planning to verify you still hit the required face velocity.
It assumes uniform velocity across the opening; real booths have dead zones and edge effects, so a compliant average CFM can still leave slow spots that trap overspray.

Current U.S. benchmarks

Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.
The producer price index for industrial chemicals stands at 344.336 (BLS, May 2026), up 16.1% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 14,543 chemical manufacturing establishments employing about 911,245 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate paint booth airflow? Multiply the booth opening area by the target face velocity, then multiply by fan and filter efficiency. A 96 ft2 opening at 100 ft/min and 90 percent efficiency gives 8,640 CFM.
What face velocity does a spray booth need? Most codes and OSHA guidance call for about 100 ft/min average face velocity at the opening for open-face and crossdraft booths, higher for some operations.
Why is my actual CFM lower than the fan rating? Loaded intake and exhaust filters, ductwork resistance, and fan wear all cut delivered airflow. The efficiency term in this calculator captures that derating.
How much airflow do dirty filters cost me? At 90 percent efficiency in the example, you lose 960 CFM off a 9,600 CFM base. As filters load further, that loss grows and face velocity drops below spec.
How do I find booth opening area? Multiply the width by the height of the working opening in feet. For a downdraft booth use the floor grate area over which air is pulled.

Last reviewed 2026-05-12.