Nozzle Number Calculator

Tell it your pump flow and the pressure you want. It tells you which nozzles to run, and what pressure you will really get.

3D render of a flat spray nozzle: threaded inlet, hex body, and a slotted tip that shapes the spray into a flat fan. — Flat spray nozzle. Threads in, hex for the wrench, slot out.

The same flat spray nozzle seen tip-on, showing the slot cut across the face. — The slot sets the fan shape. The orifice behind it sets the nozzle number.

Nozzle Planner

A triplex pump pushes a fixed flow. The nozzles decide the pressure. Size them here.

Pump Flow (GPM)

Pressure You Want (psi)

Number of Nozzles

Pump Max Pressure (psi, optional)

Total Nozzle Number Needed

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Nozzle numbers add. Five #02 nozzles act like one #10. Half sizes (#015, #025, #035…) exist but are hard to find, so the planner builds the answer from whole sizes and shows what each option does to your pressure. Mixing sizes is fine: the pump only sees the total.

Any Two, Solve the Third

Know two of nozzle number, pressure, and flow for a single nozzle? Fill them in below.

Nozzle Number

Pressure (psi)

Flow (GPM)

Enter any two values.

How It Works

Nozzle number is just flow at 4,000 psi. A #02 flows 2.0 GPM at 4,000 psi. Flow scales with the square root of pressure, so:

GPM = (N ÷ 10) × √(P ÷ 40)

Same relationship written the other way round, which is how snowmakers usually see it:

NN = 63.25 × GPM ÷ √psi

That 63.25 is just √4000. The two formulas are identical.

Worked Example

Five #02 nozzles at 1,000 psi. Each flows 1.00 GPM, so 5.00 GPM total. Nozzle number: 63.25 × 5 ÷ √1000 = 10.0.

Why square root, not double. Double the pressure and you do not double the flow. You get about 41% more. People size pumps wrong constantly because of this.

Reference Table

Flow in GPM per nozzle. Computed from the formula above. Works with JavaScript off.

Nozzle	400 psi	500 psi	700 psi	800 psi	1000 psi	1200 psi
#015	0.47	0.53	0.63	0.67	0.75	0.82
#02	0.63	0.71	0.84	0.89	1.00	1.10
#025	0.79	0.88	1.05	1.12	1.25	1.37
#03	0.95	1.06	1.25	1.34	1.50	1.64
#04	1.26	1.41	1.67	1.79	2.00	2.19
#05	1.58	1.77	2.09	2.24	2.50	2.74