Nozzle Discharge & Flow from Size & Pressure
Sizes the pump
Enter the nozzle diameter, operating pressure and discharge coefficient to get the per-nozzle flow(q = Cd·a·√(2gH)) in L/s and L/h, plus the pressure head, orifice area and jet velocity.
Rate your sprinkler nozzle
Next: plan for 961 L/h per nozzle; multiply by the number of nozzles to size the pump and mainline, and keep all heads at 2.5 bar for even coverage.
Torricelli: head H = pressure × 10.197 m/bar, exit velocity v = √(2gH), discharge Q = Cd × A × v. Higher pressure throws farther and atomises more, but raises pumping cost and drift.
Sprinkler nozzle discharge — key facts
- Discharge
- q = Cd·a·√(2gH)
- With pressure
- ∝ √pressure
- With diameter
- ∝ diameter²
- Cd
- ≈ 0.90–0.97
- 1 bar head
- ≈ 10.2 m of water
- Too low / too high
- poor spread / misting
- Units
- L/s and L/h
- Privacy
- Runs in your browser; nothing uploaded
Per-nozzle flow is the foundation of the system
A sprinkler is really just an orifice with a jet, so its flow obeys a simple law: q = Cd·a·√(2gH). The discharge rises with the orifice area — the square of the nozzle diameter — and with the square root of the operating pressure. That is why a bigger nozzle moves far more water than a higher pressure does, and why every sprinkler has a recommended pressure band: too low and the jet does not break up into an even spread, too high and it shatters into drifting mist.
This tool gives the per-nozzle discharge in L/s and L/h, the pressure head, the orifice area and the jet velocity. Knowing the flow per nozzle lets you add up the system flow to size the pump and choose the spacing that matches your soil's intake rate. Pair it with the Sprinkler System, Rain Gun Coverage and Irrigation Pump Power tools to design the full layout.
Size the pump
Add up nozzle flows to find the system flow.
Choose the right nozzle
See how diameter and pressure set the flow.
Set spacing to soil
Match application rate to the intake rate.
Avoid mist and dry spots
Stay in the nozzle's good pressure band.
Frequently Asked Questions
How is sprinkler nozzle discharge calculated?+
A nozzle behaves like an orifice, so its flow follows q = Cd·a·√(2gH): the discharge coefficient Cd, the orifice area a (from the nozzle diameter), g = 9.81 m/s², and the pressure head H. In short, flow rises with the orifice area (diameter squared) and with the square root of the operating pressure.
How does pressure affect nozzle flow?+
Flow scales with the square root of pressure, not directly. So to double the discharge you need about four times the pressure — and raising pressure from, say, 2 to 2.5 bar lifts flow by only about 12%. This is why sprinkler systems are designed around a narrow operating-pressure band rather than just turning up the pump.
How does nozzle diameter affect flow?+
The orifice area grows with the square of the diameter, and flow is proportional to area, so flow rises with the square of the diameter. A nozzle 40% larger across delivers roughly double the water at the same pressure. That makes nozzle size the strongest lever on per-sprinkler flow, ahead of pressure.
What is the discharge coefficient (Cd)?+
Cd accounts for the contraction and friction of the real jet versus an ideal orifice — actual flow is always a bit less than the theoretical maximum. For sprinkler and rain-gun nozzles it is typically 0.90–0.97; a well-rounded bore is near 0.97, a sharp-edged one nearer 0.90. The tool lets you set it for your nozzle.
Why does pressure matter for spray quality?+
Too little pressure and the jet does not break up — you get a doughnut of water near the sprinkler and dry patches. Too much pressure and the jet shatters into a fine mist that drifts on the wind and evaporates. Each nozzle has a recommended pressure band that balances throw, droplet size and uniform coverage.
How do I use this to size my pump?+
Multiply the per-nozzle discharge by the number of sprinklers running at once to get the system flow, then add the friction and elevation head to the nozzle pressure to get the total head. The pump must supply that flow at that head. Knowing per-nozzle flow first is the foundation of the whole design.
How does flow relate to sprinkler spacing?+
The application rate (mm/h) equals the nozzle flow divided by the wetted area each sprinkler covers — its spacing times the lateral spacing. Closer spacing or higher flow raises the rate; if it exceeds the soil's intake rate you get runoff. So flow and spacing are chosen together to match the soil.
What units does the tool give?+
It gives discharge in litres per second and litres per hour, plus the pressure head in metres, the orifice area in mm², and the jet velocity in m/s. L/h is handy for matching to application rate and run time; L/s is handy for adding up system flow to size the pump.
Does pressure head differ from pressure?+
Yes — pressure head is the pressure expressed as a height of water. One bar ≈ 10.2 metres of head. The discharge formula uses head H, so the tool converts your operating pressure to head internally. You can enter pressure in bar and read the equivalent head alongside the flow.
Does it run in my browser?+
Yes — all calculations happen locally in your browser. Nothing you enter is uploaded or stored, so you can design and check nozzles on a phone in the field, even offline once the page has loaded.