GPM Calculator: Pinpoint the Right Spray Nozzle Size Size

Use this GPM calculator to find the gallons per minute (GPM) per nozzle you need to hit your target application rate. Enter your GPA, nozzle spacing (inches), and travel speed (mph), and the tool outputs GPM instantly.

How to Use the GPM Calculator (3 Steps)

1. Enter GPA – Your target gallons per acre.
2. Enter Nozzle Spacing (inches) – Common boom spacings are 20 in (most field booms), 15 in (narrow), or 10 in (high-density setups).
3. Enter Speed (mph) – Your actual field speed.

Result: Required GPM per nozzle.

What is GPM?

GPM, or Gallons Per Minute, measures how much liquid your sprayer system is outputting per minute. In agriculture and turf spraying, this number helps determine application rates, ensure even coverage, and match nozzles and pumps correctly. Whether you’re calibrating for herbicide, fertilizer, or water-only applications, knowing your GPM is foundational to proper setup.

What Is This Calculator For?

This GPM (Gallons Per Minute) Calculator helps you determine the flow rate needed for your spray system under specific conditions. By inputting your system parameters (application rate, nozzle spacing, and speed), you can see exactly how many gallons per minute your sprayer will deliver.

This GPM tool will work for any sprayer application using multiple nozzles that are spaced equally across the spray bar while traveling at a constant speed. Perfect for agricultural boom sprayers, lawn sprayers, de-icing/anti-ice sprayers, dust control spray rigs, and other types of ag or industrial spray booms.

Use the GPM calculator before you spray, when designing or tuning your system, or when testing new nozzle/pressure combinations. It’s especially useful when:

• You change nozzle types or sizes.
• You adjust spray pressure.
• You want to verify that your pump and plumbing can support your desired application rate.

Knowing your GPM is essential because:

• It ensures you’re applying the correct volume for your intended coverage area.
• It allows you to determine the proper nozzle size to use and also ensure your sprayer pump/system can achieve your desired rate.
• It helps avoid under‑ or over‑application, which can waste product or reduce effectiveness.

How to Manually Check GPM

You can measure actual GPM with a bucket test:

• Catch spray from one nozzle for 1 minute.
• Measure how many gallons you captured — that’s your GPM.
• For faster results: catch for 30 seconds, then double it.

This manual test is useful for verifying calibration or spotting inconsistencies in nozzle performance. You can also check the math using this formula:

Further Tools & Resources

Knowing your Gallons Per Minute (GPM) is one of the most important steps in dialing in your spray system. Whether you’re setting up a boom sprayer, calibrating for herbicide application, or verifying if your pump and nozzles are compatible—this GPM calculator gives you a clear, fast answer based on your target GPA, nozzle spacing, and travel speed.

Once you get your GPM result, here’s what you can do next:

1. Choose the Right Nozzle Size

The GPM you just calculated is your target flow per nozzle. To find a nozzle that delivers that rate at a workable pressure, check out our Nozzle Size Guide. It walks you through orifice selection, color codes, and pressure ranges.

2. Double Check Your Application Rate

If you’re unsure whether you’re starting from the right GPA, use our reverse calculator: the GPM to GPA Converter. This helps confirm how much product you’ll be applying per acre, based on your existing setup.

3. Verify Spray Pressure

After picking a nozzle that fits your GPM, make sure you’ll be operating at a good pressure range. Use the Nozzle Pressure Calculator to find the PSI required for your chosen nozzle to hit the target flow.

4. Understand What GPA Really Means

If you’re still wrapping your head around “GPA” and how it applies in the field, check out our simple breakdown: What Does Gallons Per Acre Really Mean?. It gives real-world clarity and helps you visualize what those numbers mean on the ground.

5. Calibrate Your Speed & Pressure Together

Getting your spray system to hit the sweet spot takes more than one number. Use our Sprayer Calibration Calculator to match your target GPA with realistic speeds and nozzle pressures, so your system works in harmony.