Physics calculator

Valve Flow Coefficient Calculator

Compute incompressible liquid valve flow from Kv or Cv. Q_m³/h = Kv √(Δp_bar/SG). Kv = 0.865 Cv. Runs locally. Not a venturi, not an orifice, not Q=Av, and not Darcy.

Instant result

Result

—

Enter values to calculate.

Inputs—

Mode—

Formula—

Trust summary Engine tested · Source checked · 17/17 tests · Production surface contract 3/3 · v1.0.0

Input interpretation: Enter values to calculate.
Result: —
Model: Incompressible liquid valve flow from catalog Kv or Cv. Invert Δp, Kv, or Cv. Reports Q_m³/h.
Scope: Incompressible liquid; Q_m³/h = Kv √(Δp_bar/SG); default SG=1
Verification: Engine tested · 17/17 tests · Production surface contract 3/3 · Source checked · v1.0.0
Named expert review: Optional · Not performed
Sources: IEC 60534-1 — Industrial-process control valves — Flow capacity — Kv and the Kv–Cv relation
ISA-75.01.01 — Flow Equations for Sizing Control Valves — Liquid sizing with Cv
Sources
Evidence: 2 golden · 10 boundary · 5 property · Production surface contract 3/3 · Artifact integrity PASS
Production: Embedded snapshot: STALE · Last attested schema matched 1.0.0 snapshot / local build · Semantic contract ✓ · Last attestation PASS · current evidence changed · re-attestation required · Public/cache ✓ · Origin ✓ · Live production status PASS (0 stale; 163 CURRENT) @ 2026-09-17T06:27:56.932Z
Semantic contract: PASS

Formulas

Core equations used by this calculator.

KvQ_m³/h = Kv √(Δp_bar / SG)

ConversionKv = 0.865 Cv

SIQ = (Kv/3600) √((Δp/10⁵) / SG)

iSI. Δp in Pa, Q in m³/s. Default SG=1 (water). Kv=0.865 Cv is frozen IEC 60534-1. This page is not a venturi, not an orifice plate, not Q=Av, and not gas/choked sizing.

How to use

Enter Kv or Cv

Give one catalog coefficient, not both. Kv is m³/h at 1 bar. Cv converts with Kv=0.865 Cv.

Enter Δp in Pa

This is the valve differential. 1 bar = 10⁵ Pa. Invert for Δp, Kv, or Cv on the other tabs.

Optional SG

Leave blank for water (SG=1). Or send ρ; SG=ρ/1000. Do not send both.

Read Q

Q is m³/s. Q_m³/h is the catalog-hour rate. This is not a venturi Q=C_d A2…

Example calculations

Common configurations with formula and result.

Kv=10 at 1 bar

Kv=10, Δp=10⁵ Pa, SG=1

Q_m³/h = 10 √(1/1)

Q=10/3600 m³/s

From Cv

Cv=10/0.865, same Δp

Kv=0.865 Cv

same Q

Valve Flow Coefficient calculator specification

Version 1.0.0 · Engine tested

Calculation status

Engine tested 17/17 tests · Production surface contract 3/3
Named expert review Not performed
Calculation version 1.0.0

Review policy · Evidence

Definition: Q_m³/h = Kv √(Δp_bar / SG). Kv = 0.865 Cv (IEC 60534-1). SI reports Q in m³/s and Δp in Pa. Default SG = 1.
What it calculates: Incompressible liquid valve flow from catalog Kv or Cv. Invert Δp, Kv, or Cv. Reports Q_m³/h.
Inputs: mode?
Kv|Cv
dP|Q
SG?
rho?
Outputs: Q
Q_m3_h
dP
SG
Kv
Cv
k
Formula: Q_m³/h = Kv √(Δp_bar/SG)
Assumptions: Incompressible liquid; Q_m³/h = Kv √(Δp_bar/SG); default SG=1
Kv = 0.865 Cv (IEC 60534-1); frozen, not a US-gpm engine
Not gas, not choked, not IEC 60534-2-1 xT/Y
Not a venturi, not an orifice, not Q=Av, not Darcy, not minor-loss K
Units: SI; Q in m³/s; Δp in Pa; Kv in m³/h at 1 bar; SG dimensionless
Boundary conditions: missing Kv/Cv, Δp, or Q when required → MISSING_REQUIRED_INPUT
Kv, Cv, Δp, Q, or SG ≤ 0 → VALUE_MUST_BE_POSITIVE
Kv and Cv, SG and ρ, D1/D2, C_d, K, A, v, or Q with flow → MIXED_INPUT_ENCODING
venturi, orifice, darcy, or Q=Av as mode → INVALID_MODE
Example: Kv=10 dP=1e5 → Q=10/3600
Validation cases: 3 published on this page · 17/17 tests · Production surface contract 3/3 · View evidence
Kv=10 dP=100000 → Q=10/3600
Cv=10/0.865 dP=100000 → same Q
mode=venturi Kv=10 dP=100000 → INVALID_MODE
Sources: IEC 60534-1 — Industrial-process control valves — Flow capacity — Kv and the Kv–Cv relation
Supports: Kv is m³/h of water at 1 bar; Kv = 0.865 Cv; this page is liquid incompressible only
ISA-75.01.01 — Flow Equations for Sizing Control Valves — Liquid sizing with Cv
Supports: Incompressible liquid Q ∝ Cv √(ΔP/G); gas and choked corrections are out of scope here
Calculation version: 1.0.0

Background

Interpretation and common distinctions.

Compute incompressible liquid valve flow from catalog Kv or Cv.

Supported and not supported

Supported — Q from Kv or Cv and Δp · invert Δp, Kv, or Cv · SG or ρ · API physics.fluid.valve_cv

Not supported — venturi D1/D2, orifice C_d, Q=Av, Darcy, minor-loss K, gas/choked IEC 60534-2-1

Agent / API notes

Capability id: physics.fluid.valve_cv · tool id: valve-flow-coefficient · pin 1.0.0.

{ "Kv": 10, "dP": 100000 }

From Cv: { "Cv": 11.560693641618497, "dP": 100000 }. Optional "SG". Modes: flow (default), pressure, Kv, Cv. Errors: MISSING_REQUIRED_INPUT, INVALID_NUMBER, VALUE_MUST_BE_POSITIVE, MIXED_INPUT_ENCODING, INVALID_MODE.

Calculator URL stays /calc/physics/valve-flow-coefficient. There is no /calc/fluid.

Other calculators in this family: Venturi meter, Orifice discharge, Minor loss, Flow rate .

}

Frequently asked questions

Key distinctions behind the calculation.

Is this a venturi meter?

No. A converging–throat Bernoulli meter is /calc/physics/venturi. Sending D1 or D2 is MIXED_INPUT_ENCODING.

Is this an orifice?

No. Tank or plate Q=C_d… is /calc/physics/orifice-discharge. Sending C_d is MIXED_INPUT_ENCODING.

Is this Q = A·v?

No. Volumetric flow from area and velocity is /calc/physics/flow-rate. Sending A or v is MIXED_INPUT_ENCODING.

Do you size gas or choked valves?

No. IEC 60534-2-1 gas expansion and choked flow (xT, Y) are out of scope.

Where does this run?

Locally in the browser by default. REST and MCP call the same fluid-engine valveFlowCoefficient wrapper.