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Fertilizer Calculator

The most important and measureable nutrient components of a fertilizer, either organic or not, commercial or not, are the elements nitrogen, phosphorus, and potassium. These are identified by the three letters that are their chemical symbol, N, P and K. They are listed on commercial fertilizer containers as N-P-K and represent the percentages of each. That is, a fertilizer that is listed as 10-6-4 has 10% nitrogen, 6% phosphorous and 4% potassium.

Application quantities, however, are usually some quantity of the fertilizer per some area. This can be pounds per square foot, or pounds per 100 square feet or even cups per square foot. Converting the percentage of individual nutrient in the fertilizer to application quantities often takes some laborious calculation. This page helps with that.

Fertilizer Content

From the numbers for the fertilizer, enter the Nitrogen-Phosphorus-Potassium (N-P-K) values.

N:             P:             K:  

Desired Application Rate

Enter only one Desired Application Rate.

N:   pounds      P:   pounds           K:   pounds    per

Area for Application

Area of Application:  


Some fertilizers give a "cups to pounds" value so that the amount of fertilizer can be measured using a measuring cup. If you would prefer to display the Amount to Apply in cups rather than pounds, change the box below.

Cups to pounds conversion:  

Amount to Apply





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