Fertilizer Nutrient Conversion Calculator
Calculate N, P₂O₅ and K₂O supplied by a fertilizer quantity, plus elemental P/K equivalents and a reverse N requirement.
Convert fertilizer analysis into nutrient amounts
Calculate N, P₂O₅ and K₂O supplied by a fertilizer quantity, plus elemental P/K equivalents and a reverse N requirement.
How the fertilizer nutrient conversion calculator works
Multiplying product quantity by each guaranteed analysis percentage gives the declared nutrient amount. The tool also shows common oxide-to-element conversion factors for phosphorus and potassium and reverses the nitrogen calculation when a target N amount is entered.
When to use this farm calculation
Use this calculator when translating an N-P₂O₅-K₂O fertilizer grade into nutrient kilograms, checking a fertilizer plan, or comparing recommendations that use elemental P/K with labels that use oxide equivalents.
Inputs, units and assumptions
The calculator does not decide how much nutrient a crop needs. Soil tests, yield targets, nutrient availability, placement and local agronomic recommendations still matter. Confirm whether your local recommendation is expressed as P, P₂O₅, K or K₂O before converting.
Practical example
Applying 100 kg of a 20-20-20 product supplies 20 kg each of N, P₂O₅ and K₂O. The 20 kg P₂O₅ corresponds to about 8.73 kg elemental P.
Read fertilizer labels before converting nutrients
This fertilizer nutrient conversion calculator works from the guaranteed analysis on the product label, so the percentage entered should match the nutrient basis actually stated by the manufacturer. A 46% nitrogen fertilizer, for example, contains 46 units of nitrogen per 100 units of product by weight. Phosphate and potash grades may be expressed as P2O5 and K2O rather than elemental phosphorus and potassium. Do not substitute one basis for another without the appropriate conversion because that can materially change the application-rate estimate.