Cubic feet per minute to air changes per hour
Type a value in CFM to get it in ACH instantly.
25.49ACH
That's 1.02× as airy as an operating theatre — nothing on our list beats it. One complete change of air takes about 2.354 minutes.
Convert the other way: ACH to CFM
What it means
How fast is the air changing?
Air changes assume the incoming air mixes completely. In practice some of it short-circuits straight to the extract, so the effective rate is lower.
The math
How to convert CFM to ACH
Air changes are flow divided by room volume: ACH = m³/h ÷ room volume. The figures below use the room selected above.
Example: 150 CFM = 25.4852 ACH.
The table below is for Bathroom (10 m³).
Every unit
Your ventilation in every unit
Tables
CFM to ACH conversion table
| CFM | ACH |
|---|---|
| 0.5 CFM | 0.0849506 ACH |
| 1 CFM | 0.169901 ACH |
| 2 CFM | 0.339802 ACH |
| 3 CFM | 0.509703 ACH |
| 4 CFM | 0.679604 ACH |
| 6 CFM | 1.01941 ACH |
| 8 CFM | 1.35921 ACH |
| 10 CFM | 1.69901 ACH |
| 12 CFM | 2.03881 ACH |
| 15 CFM | 2.54852 ACH |
| 20 CFM | 3.39802 ACH |
ACH to CFM conversion table
| ACH | CFM |
|---|---|
| 0.5 ACH | 2.94289 CFM |
| 1 ACH | 5.88578 CFM |
| 2 ACH | 11.7716 CFM |
| 3 ACH | 17.6573 CFM |
| 4 ACH | 23.5431 CFM |
| 6 ACH | 35.3147 CFM |
| 8 ACH | 47.0862 CFM |
| 10 ACH | 58.8578 CFM |
| 12 ACH | 70.6293 CFM |
| 15 ACH | 88.2867 CFM |
| 20 ACH | 117.716 CFM |
Quick answers
Quick answers
- How many ACH is 1 CFM?
- 1 CFM is 0.169901 ACH.
- How many ACH is 10 CFM?
- 10 CFM is 1.69901 ACH.
- How many ACH is 150 CFM?
- 150 CFM is 25.4852 ACH.
The units
About these units
Cubic feet per minute (CFM)
How US fans are rated. One CFM is 1.7 m³/h.
Air changes per hour (ACH)
How ventilation standards are written: whole room volumes an hour.
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