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Fertilizer Calculator

Use the product label’s N-P₂O₅-K₂O percentages to calculate nutrient amounts, or enter your own application rate and area to estimate product quantity. This tool does not recommend a rate.

Use the exact guaranteed-analysis percentages and a rate you selected from the product label or qualified local guidance. Labels use N-P₂O₅-K₂O; phosphate and potash values are oxide-equivalent label amounts, not elemental phosphorus and potassium masses. This tool does not recommend rates, fertilizer, crops, timing, soil amendments or nutrient targets, and does not assess runoff or local requirements.

How do I calculate fertilizer nutrients from an NPK label?

Multiply the fertilizer mass by each label percentage and divide by 100. For example, 10 kg of product labeled 20% nitrogen contains 2 kg nitrogen. In area mode, product quantity comes from the rate and area you enter; nutrient masses then use the same label calculation.

Frequently asked questions

How do I calculate fertilizer nutrients from an NPK label?

Multiply the fertilizer mass by each label percentage and divide by 100. For example, 10 kg of product labeled 20% nitrogen contains 2 kg nitrogen. In area mode, product quantity comes from the rate and area you enter; nutrient masses then use the same label calculation.

Are fertilizer amounts or area uploaded?

No. All calculations run locally in this browser; your inputs are not sent to a server or saved by this tool.

How much nitrogen is in 10 kg of fertilizer labeled 20% N?

10 kg × 20 ÷ 100 = 2 kg of labeled nitrogen.

Does this calculator tell me how much fertilizer my plants need?

No. It only applies the label percentages to a product mass or a rate and area you enter. Use the product label, soil test and qualified local guidance to choose an application rate.