Flow Rate Estimator


Engineering Tools — Most Used

Flow Rate
Estimator

Enter a known flow rate at a catalog reference pressure to estimate the flow at your actual operating pressure. Based on the standard spray nozzle flow-pressure relationship: Q₂ = Q₁ × √(P₂ ÷ P₁).

The flow rate listed in the nozzle catalog or datasheet
The pressure at which the catalog flow rate is specified — most commonly 40 PSI
Common reference pressures
20 PSI 40 PSI 60 PSI 80 PSI 3 bar

Actual pressure at the nozzle inlet — measure under flow conditions, not static
Quick select
30 PSI 50 PSI 60 PSI 80 PSI 100 PSI

For total system flow demand. Enter 1 for single-nozzle result only.

Enter catalog flow rate, reference pressure, and your operating pressure — then tap Calculate.

Estimated Results
— GPM Flow rate at your operating pressure
All units
— GPM (US)
— L/min
— GPH
— m³/hr
Planning estimate only. Actual flow depends on nozzle condition, liquid viscosity, and stable supply pressure. Verify with a flow test before finalizing specifications.
How It Works

The Flow-Pressure Formula

For hydraulic spray nozzles, flow rate scales with the square root of operating pressure — not linearly. This formula converts any catalog flow rate to a flow estimate at a different pressure.

Formula Used by This Tool Q₂ = Q₁ × √(P₂ ÷ P₁)

Q₁ = known catalog flow rate | P₁ = catalog reference pressure | Q₂ = estimated flow at new pressure | P₂ = your operating pressure

All pressures must be in the same unit. The result is in the same unit as Q₁. This tool converts units automatically so you can mix PSI, bar, and kPa entries.

Three Common Examples

System above catalog pressure Q₁ = 1.5 GPM at P₁ = 40 PSI P₂ = 60 PSI (your system) Q₂ = 1.5 × √(60/40) Q₂ = 1.5 × 1.225
Q₂ ≈ 1.84 GPM (+23%)
System below catalog pressure Q₁ = 2.0 GPM at P₁ = 40 PSI P₂ = 25 PSI (after pipe losses) Q₂ = 2.0 × √(25/40) Q₂ = 2.0 × 0.791
Q₂ ≈ 1.58 GPM (−21%)
8-nozzle manifold, total demand Q₁ = 1.2 GPM at P₁ = 40 PSI P₂ = 50 PSI, N = 8 nozzles Q₂ = 1.2 × √(50/40) = 1.34 GPM Total = 8 × 1.34 GPM
Total ≈ 10.7 GPM

Flow Multipliers at Common Pressures

Multiply the catalog GPM by the multiplier to estimate flow at any listed pressure. Catalog reference = 40 PSI (★).

Operating Pressure In bar Flow Multiplier % Change Visual
10 PSI 0.69 bar 0.50× −50%
20 PSI 1.38 bar 0.71× −29%
30 PSI 2.07 bar 0.87× −13%
40 PSI ★ 2.76 bar 1.00× —
50 PSI 3.45 bar 1.12× +12%
60 PSI 4.14 bar 1.22× +22%
80 PSI 5.52 bar 1.41× +41%
100 PSI 6.89 bar 1.58× +58%
150 PSI 10.34 bar 1.94× +94%
200 PSI 13.79 bar 2.24× +124%

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