PC Airflow Calculator
PC Airflow Calculator compares each intake and exhaust fan in your case, then shows whether the planned airflow leans toward intake, exhaust, or a close balance.
Build Your Fan List
Use one row for each fan. Leave the planning airflow at 100% when you only want to compare rated CFM. Lower it only when you have a fan curve, a measurement, or a cautious estimate for reduced speed or a restricted mount.
What Your Fan Balance Results Mean
Enter every case or radiator fan on its own row. The tool adds the intake and exhaust ratings, applies any planning percentage you choose, and compares the two sides.
- Rated totals show the CFM printed in the fan specifications.
- Planning totals let you reduce that rating for a slower fan speed or a restricted mount.
- Airflow bias shows which side has the larger planning total. It is not a pressure measurement or a temperature forecast.
How the Totals Are Calculated
Each fan's planning CFM is its rated CFM multiplied by the planning percentage. The calculator adds all intake fans and all exhaust fans, then subtracts exhaust from intake to show the net planning airflow.
The intake-to-exhaust ratio is planning intake divided by planning exhaust. A setup with no exhaust airflow has no useful ratio. When the two planning totals differ by 5% or less, the result is labeled near balanced.
How Restrictions and Fan Speed Change Airflow
A fan's listed CFM is a maximum airflow rating from a test setup. A filter, grille, radiator, or lower fan speed can reduce the airflow in a real case. The Noctua airflow guide explains how resistance and pressure affect fan airflow.
Use 100% when you only want to compare fan ratings. Reduce the planning percentage when you have a fan curve, a test result, or a careful estimate for a known restriction. The calculator does not add a hidden correction.
How to Find a Fan's CFM Rating
Find the exact model number on the fan label, product box, or purchase record. Then check the manufacturer's page for that exact model. Fans that look alike can have different maximum speeds and airflow ratings. A manufacturer's fan specifications page shows the type of CFM figure to enter.
How to Test the Airflow After the Calculation
Run the same game or stress test before and after a change. Record CPU and graphics card temperatures, use repeatable fan speeds, and change one setting at a time. A fan curve guide can help you choose speed settings that match temperature.
More intake airflow can help filtered air enter through the intended openings. More exhaust airflow may improve heat removal in some case layouts. The best choice depends on the case, filters, coolers, and fan positions. This case setup guide shows common airflow layouts and their tradeoffs.
Want to place parts and compare estimated air paths? Use the PC airflow simulator. For help with fan direction, placement, and testing, read the PC airflow optimization guide.