Spray Mix Calculators Gallons Per Acre Calculator

Gallons Per Acre (GPA) Calculator

Convert GPA to any unit, calculate GPA from nozzle flow rate, or plan tank refills — all in one place. Enter your values and results update instantly.

On this page: Calculator · What is GPA · How to calculate · Worked example · Conversion table · FAQ

Measure your actual GPA: Sprayer Calibration · Nozzle output: Nozzle Flow Rate · Mix amounts: Spray Mix Calculator · Convert oz/acre to oz/gal: Oz Per Gallon Calculator

Calculator

GPA Converter, GPM → GPA & Coverage Planner

Choose a mode: GPA Converter to convert a known rate to all units · GPM → GPA to calculate GPA from flow rate, speed & swath · Coverage Planner to find acres per tank and refills needed.

Enter a GPA value to instantly see all equivalent rates in other units.

Enter a GPA value above to see conversions.

Don't know your GPA yet? Use the Sprayer Calibration Calculator to measure it.

Two-way converter. Choose a direction:

Formula: GPA = (GPM × 5,940) ÷ (MPH × swath inches)

Enter values above to calculate.

Example: 0.4 GPM nozzle at 5 MPH, 20-inch spacing

GPA = (0.4 × 5,940) ÷ (5 × 20) = 2,376 ÷ 100 = 23.76 GPA. That's 0.546 gal/1,000 sq ft or 222.2 L/ha. An 8-nozzle boom at this rate delivers 3.2 GPM total flow.

Example: target 15 GPA at 5 MPH, 20-inch spacing — what GPM do I need?

Switch to GPA → GPM mode. GPM = (15 × 5 × 20) ÷ 5,940 = 1,500 ÷ 5,940 = 0.252 GPM per nozzle. Check your nozzle chart at operating pressure — if your current tip flows 0.4 GPM, you'd need to increase speed or fit a smaller nozzle.

Don't know your GPM? Use the Nozzle Flow Rate Calculator to measure it from a catch test.

Need your GPM? Use the Nozzle Flow Rate Calculator. Need your MPH? Use the Sprayer Calibration Calculator.

Know your GPA and tank size? Find out how many acres you can cover per fill, and how much total mix you need for a target area.

Enter GPA and tank size above.

Example: 100-gallon tank at 20 GPA — 25-acre job

Acres per tank: 100 ÷ 20 = 5 acres per fill. Total mix needed: 25 × 20 = 500 gallons. Tank fills required: 500 ÷ 100 = 5 fills (exact). Mix product for each 100-gallon tank fill separately — don't pre-mix the full 500 gallons unless you have a nurse tank.

Example: 4-gallon backpack at 40 GPA — 0.5 acre lawn

Acres per tank: 4 ÷ 40 = 0.1 acre per fill. Total mix needed: 0.5 × 40 = 20 gallons. Tank fills: 20 ÷ 4 = 5 fills. At 40 GPA, a backpack sprayer covers about 4,356 sq ft per tank — enough for a medium-sized lawn section per fill.

Once you know total mix needed, use the Spray Mix Calculator to calculate exact concentrate per tank fill. Need a backpack sprayer? See our recommended 4-gallon backpack sprayer.

Once you know total mix needed, use Spray Coverage Calculator to plan product amounts per tank.

What is GPA?

GPA stands for gallons per acre — the total volume of spray mix applied over one acre of area. It is the standard way to describe application rate in the US for field, lawn, and agricultural spraying.

Most product labels specify a dose in ounces or pounds per acre, but that tells you nothing about how much water to use. GPA fills that gap: it defines the total gallons of water per acre (carrier volume) so the product is diluted correctly and distributed evenly across the target. Get GPA wrong and you either under-apply (poor coverage) or over-apply (wasted product and drift risk).

GPA is also commonly called application rate, carrier volume, or spray volume per acre — they all mean the same thing.

Why GPA matters

How to calculate GPA (three methods)

Method 1 — Calibration run (most accurate)

Spray a measured test strip with water, collect the volume used, then compute:

GPA = (gallons used × 43,560) ÷ (test distance ft × swath width ft)

The Sprayer Calibration Calculator does this automatically and also outputs gal/1,000 sq ft, L/ha, and travel speed.

Method 2 — From GPM, speed, and swath (boom sprayers)

If you know your nozzle flow rate from a nozzle chart or catch test:

GPA = (GPM × 5,940) ÷ (MPH × nozzle spacing in inches)

Use the GPM → GPA tab in the calculator above to run this automatically.

Method 3 — Convert from another unit

Already know your rate in gal/1,000 sq ft or L/ha? Use the GPA Converter tab to switch between units instantly.

Worked example — ATV boom sprayer

Here's a real-world scenario showing how to use all three tabs together.

Setup: ATV boom sprayer, 8 nozzles spaced 20 inches apart, travelling at 5 MPH. Each nozzle flows 0.4 GPM at operating pressure. Tank holds 100 gallons. Job is 25 acres.

Step 1 — Find GPA (GPM → GPA tab)

Enter: 0.4 GPM · 5 MPH · 20-inch swath. Formula: (0.4 × 5,940) ÷ (5 × 20) = 23.76 GPA. That's 23.76 gallons of water per acre delivered at this speed and nozzle size.

Step 2 — Check all unit equivalents (Convert GPA tab)

Enter 23.76 GPA. Results: 0.546 gal/1,000 sq ft · 222.2 L/ha. If your label specifies a minimum of 200 L/ha, you're within range. If it requires 250 L/ha, you'd need to slow down, increase pressure, or switch to a higher-output nozzle.

Step 3 — Plan refills (Coverage Planner tab)

Enter: 23.76 GPA · 100-gallon tank · 25-acre target. Results: 4.21 acres per tank · 594 gallons total · 6 fills (5 full + a partial). Now you can mix product per tank knowing exactly how many tanks you'll need.

Step 4 — Verify GPM if you change your target rate (GPA → GPM)

Say your label wants a minimum of 15 GPA. Switch Tab 2 to GPA → GPM, enter 15 GPA · 5 MPH · 20-inch swath. Required nozzle flow: 0.252 GPM. Check your nozzle chart — if your current nozzle is 0.4 GPM at that pressure, you'd need to either increase speed or fit a smaller nozzle tip.

Try it yourself: the calculator above is live — enter your own numbers in each tab.

GPA conversion table

Conversion Formula Example (20 GPA)
GPA → gal/1,000 sq ft ÷ 43.56 ≈ 0.459 gal/1,000 sq ft
GPA → L/ha × 9.354 ≈ 187.1 L/ha
GPA → L/100 m² × 0.9354 ≈ 18.71 L/100 m²
gal/1,000 sq ft → GPA × 43.56 0.5 gal/1,000 sq ft ≈ 21.78 GPA
L/ha → GPA ÷ 9.354 200 L/ha ≈ 21.38 GPA

Enter any GPA into the GPA Converter tab above for instant results.

Typical GPA ranges (rule-of-thumb)

GPA varies widely with equipment, nozzle type, and application method. These are rough reference ranges — always calibrate your own setup rather than relying on them.

Calibrate your setup and use your measured values — generic ranges won't tell you if your sprayer is actually applying what you intend.

Tools for accurate GPA measurement

GPA is only as accurate as your inputs. These are the tools that make nozzle output and pressure measurement reliable in the field:

Some links are affiliate links. Using them supports this site at no extra cost to you.

Frequently asked questions

What does GPA mean in spraying?

GPA means gallons per acre — the total spray volume applied across one acre. It is used to plan coverage, predict refills, and calibrate equipment.

How do I convert GPA to gallons per 1,000 sq ft?

Divide GPA by 43.56 (since an acre is 43,560 sq ft). Example: 20 GPA ÷ 43.56 ≈ 0.459 gal per 1,000 sq ft. Or use the GPA Converter tab above.

How do I convert GPA to L/ha?

Multiply GPA by 9.354. Example: 20 GPA × 9.354 ≈ 187.1 L/ha.

How do I convert GPA to GPM?

Rearrange the standard formula: GPM = (GPA × MPH × swath inches) ÷ 5,940. Example: 20 GPA at 5 MPH with a 20-inch nozzle swath = (20 × 5 × 20) ÷ 5,940 = 0.337 GPM per nozzle. Use the GPM ↔ GPA tab above and select GPA → GPM to calculate this automatically.

How many gallons of water per acre should I use?

The right gallons of water per acre depends on your product label, equipment, and target. Most broadcast boom sprayers run 10–40 GPA. Backpack and handheld sprayers typically apply 20–80 GPA due to slower pace and narrower swath. High-volume applications (trees, dense brush) may need 50–200+ GPA. Always check the label for a stated minimum carrier volume — some products require a specific GPA range to perform correctly.

How do I calculate GPA from GPM?

Use: GPA = (GPM × 5,940) ÷ (MPH × swath in inches). For example: 0.4 GPM at 5 MPH with a 20-inch swath = (0.4 × 5,940) ÷ (5 × 20) = 23.76 GPA. Use the GPM → GPA tab to calculate this automatically.

How many acres will my tank cover?

Divide your usable tank volume by your GPA. Example: 100-gallon tank at 20 GPA = 5 acres per fill. The Coverage Planner tab calculates this — and number of refills for a target area.

Do I need to calibrate if I'm spot spraying?

Yes. Even for spot treatments, knowing your output and walking speed helps you apply consistently and avoid over-application.

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