Assuming you had a soil test done recently, you would have received a report outlining how much fertilizer to apply.

For example, if you had a centipede lawn, perhaps the report would have said to apply 1 lb of 46-0-0 per 1000 square feet.

If you do not have a 46-0-0 fertilizer or would like the units expressed differently (lbs per acre or lbs per 5000 square feet), the calculator can adjust the recommended rates for whichever type of fertilizer you do have.

Lets assume the following for an example:
The soil report recommends 1 pound 46-0-0 per 1000 square feet.
You only have 20-0-0 and your lawn is 5000 square feet.

For example, if you had a centipede lawn, perhaps the report would have said to apply 1 kg of 46-0-0 per 100 square meters.

If you do not have a 46-0-0 fertilizer or would like the units expressed differently (kg per hectare or kg per 500 square meters), the calculator can adjust the recommended rates for whichever type of fertilizer you do have.

Lets assume the following for an example:
The soil report recommends 1 kilogram 46-0-0 per 100 square meters.
You only have 20-0-0 and your lawn is 500 square meters.

Go to Step 1. Enter fertilizer requirements.

Select the 2nd option: "a specific grade"

Then in the yellow boxes below that: enter 1 in the first box and 46-0-0 in the 2nd.

This tells the calculator that you were told in the soil report to apply 1 pounds of 46-0-0.

This tells the calculator that you were told in the soil report to apply 1 kilogram of 46-0-0.

You can also change how you would like the fertilizer recommendations expressed. You can select ounces or pounds per # of square feet or acres. If your yard is a circle and you do not know the square feet, you can click Calculate area and select the Circle tab and enter in the diameter. The program will then calculate the equivalent square feet.

You can also change how you would like the fertilizer recommendations expressed. You can select kilograms per # of square meters or hectares. If your yard is a circle and you do not know the square meters, you can click Calculate area and select the Circle tab and enter in the diameter. The program will then calculate the equivalent square meters.

In our example, we want to replace 1000 with 5000 to indicate that we want to know how much fertilizer to apply over 5000 square feet.

In our example, we want to replace 100 with 500 to indicate that we want to know how much fertilizer to apply over 500 square meters.

Go to Step 2. Select available grades.

In this section, select what fertilizers you have. Note in this section, there is a long list of different fertilizer grades you can select from (you can select lawns and gardens or farm use). If you do not have any of the specific formulations listed, you can enter what you do have at the bottom. For this example, let's say you have 20-0-0. You can enter that in the table at the bottom of Step 2, underneath "Fertilizer grades".

The output will then tell you how much 20-0-0 to apply over 5000 square feet. In this case, you would want to apply 11.5 lbs of 20-0-0 over 5000 square feet.

The output will then tell you how much 20-0-0 to apply over 500 square meters. In this case, you would want to apply 11.5 kg of 20-0-0 over 500 square meters.

The Score
The score represents how well a fertilizer recommendation matches the soil test report recommendation.

A perfect score is 100.
Points are deducted if the supplied nitrogen is outside 10% of N recommended, if the supplied phosphorus is too high, or if the supplied potassium or sulfur is too low.

Max grades to use in recommendation
The Fertilizer Calculator provides a recommendation based on the best combination (best score) of one or more fertilizer grades.

What shape best describes the area to be fertilized?

Length: ft
Width: ft
Area: sq ft
Length: m
Width: m
Area: sq m
Side A: ft
Side B: ft
Side C: ft
Area: sq ft
Side A: m
Side B: m
Side C: m
Area: sq m
Diameter: ft
Area: sq ft
Diameter: m
Area: sq m
Length: ft
Height: ft
Area: sq ft
Length: m
Height: m
Area: sq m
Length: ft
Height: ft
Area: sq ft
Length: m
Height: m
Area: sq m

Use this calculator to …

Convert fertilizer recommendations between pounds per acre and pounds per square feet. kilograms per hectare and kilograms per square meters.

List alternative recommendations when fertilizer grades are not available.

Get recommendations based on the specific area to be fertilized.

Calculate fertilizer costs.

Options
Show top scores
Show scores of or higher

Max grades to use in recommendation:
Round recs to the nearest:
units

Fertilizer Calculator
N-P2O5-K2O-S
R. Hitchcock and D. E. Kissel

The University of Georgia Fertilizer Calculator was developed to assist users whose fertilizer needs require adjustment from the standard soil test recommendation due to a change in units, availability of fertilizer products, and/or a difference in land size. The calculator ranks various fertilizer combinations, with the best getting the highest score.

You can use it to:

  • Calculate the weight of fertilizer materials to supply the amounts of N, P2O5, K2O, S recommended by a soil test report.
  • Select recommendations in pounds per acre that are typical of agronomic crop recommendations or in pounds per 1000 square feet that are typical of homeowners reports such as for a home lawn. Select recommendations in kilograms per hectare that are typical of agronomic crop recommendations or in kilograms per square meters that are typical of homeowners reports such as for a home lawn.
  • Select fertilizer grades different from those given in the recommendation. This is useful when the fertilizer grades in the test report are not available locally.
  • Calculate the area of a garden or lawn given the dimensions and shape of the area to be fertilized.
  • Calculate fertilizer costs.

Before blending fertilizers, check a compatibility list to ensure they can be blended safely.

How to use the calculator

Step 1. Enter fertilizer requirements

Fertilizer recommendations are given in:


Recommendation from soil test report:

pounds kilograms of per 1000 square feet 100 square meters

Example: 5 pounds of 10-10-10-5 per 1000 square feet

Example: 5 kilograms of 10-10-10-5 per 100 square meters


Application:

per    


Recommendation, lbs per acre basis
Nitrogen (N) lbs/acre
Phosphate (P2O5) lbs/acre
Potash (K2O) lbs/acre
Sulfur (S) lbs/acre
Recommendation, kilograms per hectare basis
Nitrogen (N) kg/ha
Phosphate (P2O5) kg/ha
Potash (K2O) kg/ha
Sulfur (S) kg/ha
Recommendation from
soil test report
Application
N P2O5 K2O S
pounds per acre kilograms per hectare
per

Step 2. Select available grades


Choose from the list of commonly-available grades below,
or add your own in N-P2O5-K2O-S format.

Show grades for:






































You can add your own grades and fertilizer costs below:

Fertilizer grades
(N-P2O5-K2O-S)
$ Cost per

Output will appear here:

Fertilizer recommendations based on
available grades, application rate, and area
Nutrients
supplied
Nutrients
surplus or deficit
Score Cost
NPKS NPKS