Spray Mix Calculators PSI vs GPM Calculator
PSI vs GPM Calculator: Pressure to Flow for Sprayer Nozzles
There’s no universal PSI→GPM conversion. But for the same nozzle/orifice, you can estimate flow changes with: Q₂ = Q₁ × √(P₂ / P₁). Use this page to estimate GPM at a new PSI (or required PSI for a target flow).
Best practice: estimate here → verify output with Nozzle Flow Rate → compute spray rate with Calibration → mix with Spray Mix Calculator.
Pressure ↔ Flow Reference (Same Nozzle)
Enter a baseline flow and pressure from a nozzle chart (or a catch test). Then calculate the flow at a new pressure, or the pressure needed for a target flow. Includes bar and L/min conversions.
Accuracy note: regulator settings, hose losses, clogged strainers, and nozzle wear can change real nozzle pressure/flow. Use a catch test to confirm real output.
Quick reference: how flow changes with pressure
For the same nozzle, flow scales with the square root of pressure: Q ∝ √P. Values below are approximate multipliers.
| Pressure change | Flow multiplier | Example (0.20 GPM baseline) |
|---|---|---|
| +25% pressure (× 1.25) | × 1.118 | ≈ 0.224 GPM |
| +50% pressure (× 1.50) | × 1.225 | ≈ 0.245 GPM |
| Double pressure (× 2.00) | × 1.414 | ≈ 0.283 GPM |
| Half pressure (× 0.50) | × 0.707 | ≈ 0.141 GPM |
If you need actual output (not an estimate), do a catch test using Nozzle Flow Rate.
GPM to bar: converting between US and metric pressure units
Bar is the standard pressure unit on most European and metric-spec sprayer equipment, while US equipment is typically rated in PSI. There's no direct "GPM to bar" conversion — GPM is a flow rate and bar is a pressure unit, so converting between them requires the same nozzle relationship used above: Q₂ = Q₁ × √(P₂ / P₁).
To go from a bar reading to PSI (or back), use:
Once you have your pressure in matching units, use the calculator above — just select Metric (bar, L/min) from the Units dropdown, enter your baseline bar pressure and L/min flow, then enter your target bar pressure to get the estimated flow.
Example: nozzle rated at 0.20 L/min at 2.5 bar — what's the flow at 4 bar?
Using Q₂ = Q₁ × √(P₂ / P₁): 0.20 × √(4 ÷ 2.5) = 0.20 × √1.6 = 0.20 × 1.265 = ≈ 0.253 L/min. Select Metric units above and enter these values to confirm.
FAQ
Is there a universal PSI to GPM conversion?
No. Flow depends on nozzle/orifice size and design. This page estimates how flow changes with pound per square inch pressure for the same nozzle using Q₂ = Q₁ × √(P₂/P₁).
If I double PSI, do I double GPM?
No. Doubling pressure increases gallon per minute flow by √2 (about 1.41×) for the same nozzle.
How do I estimate required PSI for a target flow?
Use P₂ = P₁ × (Q₂/Q₁)². This calculator computes it when you enter a baseline and a target flow.
Should I trust the result exactly?
Treat it as an estimate. Pressure at the nozzle can differ from gauge pressure due to losses and restrictions. Verify output with a catch test if accuracy matters.
How do I convert GPM to bar for my sprayer?
GPM and bar aren't directly interchangeable — GPM measures flow rate and bar measures pressure. First convert bar to PSI (bar × 14.5038), then use the calculator above with your baseline PSI/GPM and your target PSI to estimate the new flow. Switch the Units dropdown to Metric to work in bar and L/min directly.