CFM per Watt Calculator
Airflow efficiency of a fan in CFM delivered per watt consumed.
Enter your values
Enter the airflow in CFM.
Enter the power draw in W.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Efficiency
- 6.67 CFM/W
- Rating
- Good
- Power for 1000 CFM at this efficiency
- 150 W
Quick answer
CFM per watt equals the fan's airflow divided by its measured or rated electrical power draw.
CFM/W = CFM / Watts
At a glance
| What it does | Airflow efficiency of a fan in CFM delivered per watt consumed. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Airflow, Power draw |
| Main output | Efficiency |
| Formula | CFM/W = CFM / Watts |
| Cost | Free — no sign-up, no download |
How to use the CFM per Watt Calculator
- 1Enter the fan's rated or measured airflow.
- 2Enter its electrical power draw in watts.
- 3Compare the resulting CFM per watt against other models — higher is more efficient.
Inputs explained
- Airflow(CFM)
- Enter the airflow in CFM.
- Power draw(W)
- Enter the power draw in W.
Worked example
Using the values the calculator loads with:
Inputs
- Airflow400 CFM
- Power draw60 W
Results
- Efficiency6.67 CFM/W
- RatingGood
- Power for 1000 CFM at this efficiency150 W
Frequently asked questions
What is a good CFM/W value?
PSC motor fans often run 3-6 CFM/W, while efficient ECM/EC fans commonly exceed 8-12 CFM/W.
Does this account for static pressure?
No — always compare fans at the same operating static pressure, since CFM/W drops sharply as pressure rises.
What do I need to enter into the CFM per Watt Calculator?
Just 2 values: airflow, power draw. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the CFM per Watt Calculator work out the answer?
CFM per watt equals the fan's airflow divided by its measured or rated electrical power draw. It applies the formula CFM/W = CFM / Watts and shows the working so you can check each step by hand.
Is the CFM per Watt Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.