Velocity Pressure Calculator
Velocity pressure and equivalent velocity from a pitot reading.
Enter your values
Enter the velocity pressure in in wc.
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.
- Velocity
- 2,003 FPM
- Velocity
- 10.2 m/s
- Velocity pressure entered
- 0.25 in wc
Quick answer
Velocity in feet per minute equals 4005 times the square root of velocity pressure in inches of water at standard air density.
V = 4005 x sqrt(VP)
At a glance
| What it does | Velocity pressure and equivalent velocity from a pitot reading. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Velocity pressure |
| Main output | Velocity |
| Formula | V = 4005 x sqrt(VP) |
| Cost | Free — no sign-up, no download |
How to use the Velocity Pressure Calculator
- 1Read velocity pressure from a pitot tube and manometer or micromanometer.
- 2Enter the value here to get the equivalent air velocity.
- 3Multiply velocity by duct area to get CFM.
Inputs explained
- Velocity pressure(in wc)
- Enter the velocity pressure in in wc.
Worked example
Using the values the calculator loads with:
Inputs
- Velocity pressure0.25 in wc
Results
- Velocity2,003 FPM
- Velocity10.2 m/s
- Velocity pressure entered0.25 in wc
Frequently asked questions
Does air temperature matter?
Yes — the 4005 constant assumes standard air; correct for density at high temperature or altitude.
What if I measure velocity directly?
Use it directly; VP = (V/4005)^2 converts the other way if needed.
What do I need to enter into the Velocity Pressure Calculator?
Just 1 value: velocity pressure. 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 Velocity Pressure Calculator work out the answer?
Velocity in feet per minute equals 4005 times the square root of velocity pressure in inches of water at standard air density. It applies the formula V = 4005 x sqrt(VP) and shows the working so you can check each step by hand.
Is the Velocity Pressure 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.