What is the formula for converting actual nitrogen rates to pounds of fertilizer?
Divide the given rate of actual nitrogen by the percentage of nitrogen, expressed as a decimal, in the fertilizer grade. For example, if a gardener wants to apply 3 pounds of actual nitrogen and is using an 18-6-12 fertilizer, divide 3 by .18. This equals about 16.5 pounds of fertilizer per 1000 square feet.