Air Changes Per Hour (ACH) Calculator
Construction & Home ImprovementCalculate how many times per hour a room's air is fully replaced, from airflow rate and room dimensions.
Air Changes Per Hour
Number of times the room volume of air is fully exchanged each hour.
Found this calculator useful?
From Scratch To $10K/Month In 60 Days
This is a proven money making system that takes students by the hand to make at least $10,000 per month, every month. Students get 12 weeks of guided coaching in addition to the "MPS Super Funnel" and tools.
We value your privacy and promise not to sell or misuse your information. Here's our privacy policy.
Calculator Stats
Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
Embeds
Construction & Home Improvement calculators
Calculator Stats
Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
Embeds
Construction & Home Improvement calculators
Frequently Asked Questions
What is a good ACH value?
Recommended air changes per hour vary widely by room type, roughly 4 to 6 for a typical bedroom or living room, up to 15 or more for kitchens and bathrooms, and 20 or higher for hospitals or commercial kitchens. Check a ventilation guideline for your specific room type rather than assuming one number fits every space.
How is ACH calculated?
Airflow in cubic feet per minute is multiplied by 60 to convert to cubic feet per hour, then divided by the room volume, area times ceiling height, to get the number of full air exchanges per hour.
How is this different from the CFM calculator?
This calculator finds the ACH produced by a known airflow rate, useful for checking whether existing ventilation is adequate. The CFM calculator works the other direction, finding the airflow needed to hit a target ACH, useful when sizing a new fan or ventilation system.
Spot a mistake? Tell us what's wrong.
Request a calculator. The most-requested ones get built first in our monthly batch.
Request a calculatorWant this calculator on your website?
Embed the Air Changes Per Hour (ACH) Calculator on any site — no code needed. Customize colors, remove branding, and track usage.
