Fertilizer Rate Calculator

Turn a target amount of nitrogen into the pounds of fertilizer to spread. It works for any nutrient by using that nutrient's percentage on the bag.

How it works

A fertilizer's N-P-K label lists the percentage of each nutrient by weight, so a 10-10-10 bag is 10% nitrogen. To deliver a target amount of a nutrient, divide the target by that percentage (as a decimal), then scale to your area:

Fertilizer per 1,000 sq ft = target ÷ ( % nutrient ÷ 100 )

For example, to apply 1 lb of nitrogen per 1,000 sq ft from a 10% nitrogen product, you spread 10 lb of product per 1,000 sq ft. Use the first N-P-K number for nitrogen, the second for phosphate, or the third for potash, depending on which nutrient you are targeting.

Important limits

This is arithmetic, not an agronomic recommendation. The right target rate comes from a soil test and crop-specific guidance from your Cooperative Extension office, and over-applying nutrients wastes money and can harm water quality. Many areas have rules on nutrient timing and amounts, especially near waterways. Always follow the product label and local regulations.

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This tool is a planning aid and does the math from the numbers you enter. It is not a substitute for a soil test, seed-tag information, or advice from your local Cooperative Extension office. Page updated Aug 4, 2026.