Every valve has a Kv: the flow of water in m³/h that causes a 1 bar drop. Knowing it, you can predict the pressure drop at any flow – essential for balancing heating systems and sizing pumps.
How to use the Differential Pressure Calculator
- Liquid
- Specific gravity
- Flow rate Q
- Flow coefficient K_v (m³/h)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the liquid, enter the flow rate and the valve’s Kv.
Inputs explained
| Field | What to enter |
|---|---|
| Liquid | Choose one: Water, Seawater, Ethanol, Acetone … |
| Specific gravity | A number |
| Flow rate Q | Units: m³/h, L/min, L/s, US gpm |
| Flow coefficient K_v (m³/h) | A number |
Example values
How the main result changes when Specific gravity changes and everything else stays at the example values above:
| Specific gravity | Pressure drop ΔP (bar) |
|---|---|
| 0.5 | 0.25 |
| 0.75 | 0.25 |
| 1 | 0.25 |
| 1.25 | 0.25 |
| 1.5 | 0.25 |
| 2 | 0.25 |
Formula
ΔP (bar) = SG·(Q (m³/h) / K_v)²
Worked example
Inputs — Liquid: Water; Flow rate Q: 2 m³/h; Flow coefficient K_v (m³/h): 4.
Results — Pressure drop ΔP = 0.25 bar.
Key terms
- Differential pressure
- Pressure difference between two points.
Frequently asked questions
What is Kv?
The water flow in m³/h through a valve at 1 bar pressure drop.
How does the drop scale with flow?
With the square of the flow rate.
How do Kv and Cv relate?
Cv = 1.156·Kv.
Why is SG included?
Denser liquids produce a larger drop at the same flow.