Valve Flow Coefficient (Kv, metric)
Also known as Kv
Worked example: Kv 18 at 1 bar on water → 18 m3/h = 300 L/min — press Try an example to run it live, then adjust anything.
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Valve Flow Coefficient (Kv, metric) explained
Kv is the European twin of Cv: cubic metres per hour of water at 1 bar of pressure drop instead of gallons per minute at 1 psi. A Kv 18 valve passes 18 m³/h — 300 L/min — at 1 bar. The two coefficients differ only by unit conversion, Cv = 1.156 Kv, so a valve stamped Kv 10 is a Cv 11.6 valve; European balancing-valve charts and North American control-valve catalogues describe exactly the same hardware in these two dialects.
The practical warning is that manufacturers publish both, and mixing them silently under-sizes a valve by about 15%. Check the datasheet units before you trust a number, and beware a third variant, Av, defined in SI base units (m² of equivalent orifice) with Av = 2.4 × 10⁻⁵ Kv. On balancing valves the published Kv is also a function of handwheel position, so the catalogue table has a Kv per turn — always read at the setting you will actually commission.
Valve Flow Coefficient (Kv, metric) formula
- = Flow rate (L/min)
- = Flow coefficient (metric) (m³/(h·√bar))
- = Pressure drop (kPa)
- = Specific gravity
Missing one of these? Work it out first, then come back
- Flow rate — Pump Water Horsepower, Pump Brake Horsepower
- Flow coefficient (metric) — Valve Flow Coefficient (Cv)
- Pressure drop — Valve Flow Coefficient (Cv), Poiseuille's Law
- Specific gravity — Pump Water Horsepower, Pump Brake Horsepower