Home Liquid Fertilizer Rate Calculator

Liquid Fertilizer Rate Calculator

Calculate the exact liquid fertilizer application rate needed to deliver a target amount of nitrogen, phosphorus, or potassium. Enter the NPK analysis and fertilizer density from your label — get gallons per acre, oz per 1,000 sq ft, and lbs of each nutrient delivered. Works for broadcast, foliar, fertigation, and small-container garden applications.

⚠️ Base rates on a current soil test.

This calculator computes how much fertilizer delivers a target nutrient rate. It does not prescribe what rate to apply. Always use a soil test recommendation and follow the product label's minimum and maximum rates.

On this page: Calculator · Reading NPK labels · Common liquid fertilizer reference · Application rate guide · Related tools · FAQ

Applying fertilizer with a sprayer? Sprayer Calibration Calculator · Adding fertilizer to a tank mix? Tank Mix Calculator.

Calculator

Liquid Fertilizer Application Rate Calculator

Choose a mode: Rate Finder to calculate gal/acre from a target nutrient rate · Nutrient Checker to see lbs of N-P-K delivered by a given application rate · Small-Scale Container for 5-gallon buckets, backpack sprayers, and garden use.

Enter your fertilizer analysis and target nutrient rate to find the required application rate in gallons per acre and oz per 1,000 sq ft.

Fertilizer Product

Target Nutrient Rate

Measure smaller liquid-fertilizer volumes with a chemical measuring cup↗; for field-scale rates, use the product label and calibrated application equipment.

Already know your application rate? Enter it here to see exactly how many lbs of N, P₂O₅, and K₂O you're delivering per acre or per 1,000 sq ft.

Application Rate Applied

For garden, lawn, or small-scale use. Enter your target area, fertilizer NPK, and container size to get oz or tablespoons per container — including 5-gallon bucket and backpack sprayer amounts.

Target & Container

Tip: For precise small-volume measuring, use a measuring syringe↗ or graduated cylinder↗.

🌱 Applying liquid fertilizer with a sprayer?
Make sure your equipment is dialed in: Sprayer Calibration Calculator · Spray Tip Calculator · Nozzle Flow Rate Calculator.

How to read liquid fertilizer NPK labels

Every liquid fertilizer label includes a guaranteed analysis expressed as three numbers: N – P₂O₅ – K₂O. Understanding what these mean is essential to calculating the correct application rate.

Number Nutrient Form reported What it means
First (N) Nitrogen % elemental N by weight 28-0-0 contains 28 lbs of N per 100 lbs of product
Second (P) Phosphorus % as P₂O₅ by weight To convert to elemental P: multiply by 0.436
Third (K) Potassium % as K₂O by weight To convert to elemental K: multiply by 0.830

Why weight per gallon matters

Because liquid fertilizers are applied by volume (gallons per acre), you must know the weight per gallon (lbs/gal) to convert between volume and nutrient weight. This varies significantly by product: water weighs 8.34 lbs/gal, while 28-0-0 UAN is about 10.67 lbs/gal at 60°F in CF Industries' reference data, while Nutrien lists 10-34-0 APP at 11.6 lbs/gal at 75°F. Always find this on the product label — using the wrong density leads to significant over- or under-application.

The core formula this calculator uses:

Gal/acre = Target lbs nutrient/acre ÷ (Nutrient% ÷ 100 × lbs/gal)

Example: to apply 100 lbs N/acre with 28-0-0 UAN at 10.67 lbs/gal:
100 ÷ (0.28 × 10.67) = 100 ÷ 2.99 = 33.5 gal/acre

Liquid fertilizer weight per gallon reference

Density matters because the calculator converts product volume to nutrient weight. The values below are manufacturer reference values at the stated temperatures; your actual product label or data sheet remains the best input when it differs.

Product Analysis Reference density Approx. nutrient per gallon
UAN-28 28-0-0 10.67 lb/gal at 60°F 2.99 lb N/gal
UAN-30 30-0-0 10.86 lb/gal at 60°F 3.26 lb N/gal
UAN-32 32-0-0 11.08 lb/gal at 60°F 3.55 lb N/gal
10-34-0 APP 10-34-0 11.6 lb/gal at 75°F 1.16 lb N + 3.94 lb P₂O₅/gal

Source values: CF Industries UAN product specification (density at 60°F) and Nutrien POLY10 10-34-0 product data sheet (density at 75°F). Published densities are typical/reference values, so use your own product documentation when available.

How to choose the target liquid fertilizer rate

This calculator answers how much product is needed to deliver a target nutrient rate; it does not determine the agronomic target. Choose the target from a current soil or tissue test recommendation, a crop nutrient-management plan, a qualified agronomist or extension recommendation, and the product label.

Once you have a target such as pounds of N per acre or pounds of N per 1,000 sq ft, enter it in Rate Finder. For a small sprayer or bucket, also enter the area one full container actually covers. That calibrated coverage is what converts the total nutrient requirement into an amount per container.

Why a 5-gallon bucket does not have one universal fertilizer dose

A 5-gallon container is only a carrier volume. If one operator applies those 5 gallons over 500 sq ft and another applies them over 2,000 sq ft, the same ounces of fertilizer would deliver very different nutrient rates per area. The Small-Scale tab therefore uses both container size and calibrated area-per-container.

Sources and calculation method

The nutrient math uses guaranteed-analysis percentages by weight and product density. Reference UAN densities come from the CF Industries UAN product specification. The 10-34-0 reference comes from Nutrien's POLY10 product data sheet. Always substitute the analysis and density for the exact fertilizer you are applying.

Frequently asked questions

How do you calculate liquid fertilizer application rate?

The formula is: Gal/acre = Target lbs nutrient/acre ÷ (Nutrient% ÷ 100 × lbs/gal). For 28-0-0 UAN (10.67 lbs/gal at 60°F) to deliver 100 lbs N/acre: 100 ÷ (0.28 × 10.67) = 33.5 gal/acre. The Rate Finder tab does this automatically for any NPK analysis, density, and nutrient target.

How much liquid fertilizer do I add to a 5-gallon bucket?

There is no single dose based on bucket size alone. You need the fertilizer's N analysis and density, your target nutrient rate, and the area one full 5-gallon container covers. Enter those values in the Small-Scale tab to calculate total product and fl oz per full container.

How much liquid fertilizer should I give my plants?

The calculator does not prescribe a plant-specific nutrient rate. Use the product label and a soil/tissue test or local agronomic recommendation to choose the target rate, then use this page to convert that target into gallons or fluid ounces of product.

What does NPK mean on liquid fertilizer?

NPK stands for the three primary macronutrients: N (Nitrogen), P (Phosphorus, reported as P₂O₅), and K (Potassium, reported as K₂O). The guaranteed analysis numbers on the label are percentages by weight. A product labeled 28-0-0 contains 28% nitrogen by weight, no phosphorus, and no potassium.

Why does weight per gallon matter for liquid fertilizer calculations?

Liquid fertilizers are applied by volume, while guaranteed analysis is expressed by weight. Density connects those units. For example, CF Industries lists UAN-28 at 10.67 lb/gal at 60°F; using water density instead would materially misstate nutrient delivered per gallon. Use the exact product label or data sheet when available.

Can I mix liquid fertilizer with herbicide or pesticide in the same tank?

Only when the labels for all products permit the combination and the mixture is physically compatible. Follow each label's restrictions and mixing order; when the labels call for a compatibility or jar test, perform it before filling the full tank. The Tank Mix Calculator can scale amounts, but it cannot determine legal or chemical compatibility.

What is fertigation and how do I calculate the rate?

Fertigation applies nutrients through an irrigation system. Use Rate Finder to calculate the fertilizer quantity needed per acre or hectare from the chosen nutrient target, then follow the fertilizer label, irrigation-system specifications, water-quality guidance, and your nutrient-management plan for injection concentration and timing.