Air Changes per Hour Reference Values

Calculate room air changes per hour (ACH) from supply airflow and space volume.

Author

Dr. Lars Eriksson

HVAC editorial contributor

Swedish environmental economist from Stockholm School of Economics, advisor to the EU on carbon pricing policy

Reviewed for accuracy by

Prof. Rajesh Sharma

HVAC content reviewer

Indian agricultural economist from IARI New Delhi, advising governments on food security under climate change

Last updatedFebruary 22, 2026

PublishedFebruary 22, 2026

Reference Value Index

This page lists 36 reference values for quick browsing and lookup.

Back to converter page · View HTML sitemap

All Reference Values

Reference Table

Air Changes per Hour reference values
Scenario	ACH	Room Volume (ft³)
10×10×8 ft room at 100 CFM	7.5 ACH	800
10×10×8 ft room at 200 CFM	15 ACH	800
10×10×8 ft room at 300 CFM	22.5 ACH	800
10×10×8 ft room at 400 CFM	30 ACH	800
10×10×8 ft room at 600 CFM	45 ACH	800
10×10×8 ft room at 800 CFM	60 ACH	800
12×12×8 ft room at 100 CFM	5.21 ACH	1,152
12×12×8 ft room at 200 CFM	10.42 ACH	1,152
12×12×8 ft room at 300 CFM	15.63 ACH	1,152
12×12×8 ft room at 400 CFM	20.83 ACH	1,152
12×12×8 ft room at 600 CFM	31.25 ACH	1,152
12×12×8 ft room at 800 CFM	41.67 ACH	1,152
15×12×8 ft room at 100 CFM	4.17 ACH	1,440
15×12×8 ft room at 200 CFM	8.33 ACH	1,440
15×12×8 ft room at 300 CFM	12.5 ACH	1,440
15×12×8 ft room at 400 CFM	16.67 ACH	1,440
15×12×8 ft room at 600 CFM	25 ACH	1,440
15×12×8 ft room at 800 CFM	33.33 ACH	1,440
20×15×9 ft room at 100 CFM	2.22 ACH	2,700
20×15×9 ft room at 200 CFM	4.44 ACH	2,700
20×15×9 ft room at 300 CFM	6.67 ACH	2,700
20×15×9 ft room at 400 CFM	8.89 ACH	2,700
20×15×9 ft room at 600 CFM	13.33 ACH	2,700
20×15×9 ft room at 800 CFM	17.78 ACH	2,700
25×20×10 ft room at 100 CFM	1.2 ACH	5,000
25×20×10 ft room at 200 CFM	2.4 ACH	5,000
25×20×10 ft room at 300 CFM	3.6 ACH	5,000
25×20×10 ft room at 400 CFM	4.8 ACH	5,000
25×20×10 ft room at 600 CFM	7.2 ACH	5,000
25×20×10 ft room at 800 CFM	9.6 ACH	5,000
40×25×12 ft room at 100 CFM	0.5 ACH	12,000
40×25×12 ft room at 200 CFM	1 ACH	12,000
40×25×12 ft room at 300 CFM	1.5 ACH	12,000
40×25×12 ft room at 400 CFM	2 ACH	12,000
40×25×12 ft room at 600 CFM	3 ACH	12,000
40×25×12 ft room at 800 CFM	4 ACH	12,000

Frequently Asked Questions

Frequently asked questions for Air Changes per Hour and its reference values.

What is ACH in HVAC design?

ACH means air changes per hour and indicates how many times the room air volume is replaced each hour.

How is ACH calculated?

ACH = (CFM × 60) / room volume in cubic feet.

Can I calculate required CFM from target ACH?

Yes. Rearranging gives CFM = (ACH × room volume) / 60.

Is higher ACH always better?

Not always; target ACH depends on occupancy, use type, comfort, and energy goals.

Methodology and Review

Each row on this page links to a value detail page derived from the same conversion data file as the main calculator and reference table. This reduces inconsistencies across page variants.

Editorial metadata and structured data are rendered across the converter page and linked value pages. Review policies are documented in our review process and editorial policy.