Skip to main content
SimuPipe

Cv to Kv Conversion Table

Convert between the valve flow coefficients Cv (US/imperial) and Kv (metric), with a quick-reference conversion table, US vs UK Cv, the IEC 60534 sizing equation, and representative full-open Cv values by valve type. Both coefficients measure how much flow a valve passes for a given pressure drop.

Conversion Factors
Kv=0.865 CvK_v = 0.865 \, C_v
Cv=1.156 KvC_v = 1.156 \, K_v
Cv,UK=0.962 KvC_{v,\text{UK}} = 0.962 \, K_v

Cv (US) is the flow of water in US gpm at 60 °F through the valve at 1 psi drop; Kv is m³/h at 5-30 °C at 1 bar drop. UK Cv uses imperial gallons (Kv=1.039 Cv,UKK_v = 1.039 \, C_{v,\text{UK}}).

Cv ↔ Kv Conversion Table
Kv (m³/h·bar)Cv (US)Cv (UK)
11.160.96
22.311.92
55.784.81
1011.69.62
2528.924.1
5057.848.1
10011696.2
250289241
500578481
10001156962

Need a specific value? Use the interactive valve sizing calculator to convert any Cv, Kv, or UK Cv and to size for liquid or gas.

Liquid Sizing Equation (IEC 60534)

For turbulent, non-choked liquid flow, the required coefficient is:

Cv=QSGΔPKv=QSGΔPC_v = Q \sqrt{\frac{SG}{\Delta P}} \qquad K_v = Q \sqrt{\frac{SG}{\Delta P}}
  • QQ — flow rate (US gpm for Cv; m³/h for Kv)
  • ΔP\Delta P — pressure drop across the valve (psi for Cv; bar for Kv)
  • SGSG — specific gravity of the fluid (water = 1)

Compressible (gas) and choked flow use the fuller IEC 60534 method with an expansion factor Y and pressure-drop ratio xT — handled by the valve sizing calculator.

Representative Full-Open Cv by Valve Type
SizeGlobeBall (full port)ButterflyGate
1/2"815—20
1"1855—55
2"55280110280
4"20013005001100
6"450300011002500

Representative US Cv at full open, order-of-magnitude only — actual values vary widely by manufacturer, port style, and trim. Use these to compare valve types, never to size; always size from the manufacturer's published Cv for the specific valve and opening.

Frequently Asked Questions

What is the difference between Cv and Kv?
Both are valve flow coefficients that measure how much flow a valve passes for a given pressure drop — a larger number means less restriction. Cv is the US/imperial coefficient: the flow of water in US gallons per minute at 60 °F that passes through the valve with a 1 psi pressure drop. Kv is the metric coefficient: the flow of water in cubic metres per hour at 5-30 °C with a 1 bar pressure drop. They describe the same valve, just in different units.
How do I convert Cv to Kv?
Multiply Cv by 0.865 to get Kv, or multiply Kv by 1.156 to get Cv (using US Cv). For example, a valve with Cv = 10 has Kv ≈ 8.65, and a valve with Kv = 10 has Cv ≈ 11.56. These factors come from the unit conversion between US gpm/psi and m³/h/bar for water.
What is the difference between US Cv and UK Cv?
US Cv uses US gallons per minute; UK (imperial) Cv uses imperial gallons per minute, which are about 20% larger. As a result the conversion factor differs: Kv = 1.039 × Cv(UK), so Cv(UK) ≈ 0.962 × Kv, whereas Cv(US) ≈ 1.156 × Kv. Always check whether a published Cv is US or UK — most modern valve data and IEC 60534 use US Cv or Kv.
What is a typical Cv for a 2-inch valve?
It depends heavily on the valve type. A 2-inch globe valve might be around Cv 55, while a 2-inch full-port ball valve can be 250-300 because it has a near-straight-through bore. Butterfly and gate valves fall in between to high. The representative table on this page shows the relative magnitudes, but you must use the manufacturer's published Cv for the specific valve and opening when sizing.
How is Cv used to size a valve?
For incompressible (liquid) flow, the required coefficient is the flow divided by the square root of the pressure drop scaled by specific gravity: Cv = Q·√(SG/ΔP) in US units, or Kv = Q·√(SG/ΔP) in metric units. You compute the required Cv/Kv for your duty, then pick a valve whose rated coefficient comfortably exceeds it. Gas and choked-flow sizing use the fuller IEC 60534 method with an expansion factor — see SimuPipe's valve sizing calculator.
Is a valve's Cv constant?
No. The published 'rated Cv' is the value at full open. As the valve closes, its effective Cv drops along its inherent flow characteristic (linear, equal-percentage, or quick-opening), so a control valve operating at part travel has a much lower Cv than its rated figure. Size control valves so the duty point sits in the controllable mid-travel range, not near fully open or fully shut.

Size control valves with SimuPipe

Convert Cv ↔ Kv and size valves for liquid or gas (IEC 60534) — free, in your browser.

Get Started FreeValve Sizing Calculator

Related

Valve Sizing CalculatorControl Valve Sizing (IEC 60534)Pipe Roughness (ε)Hazen-Williams C-Factor