Calculate how much nitrogen, phosphorus, and potassium a fertilizer supplies. Estimate N-P-K pounds, ounces, nutrient ratio, fertilizer needed from a target nutrient amount, bags needed, cost, and garden coverage.
Nutrients from fertilizer mode:
The calculator multiplies fertilizer amount by the N-P-K percentages to estimate nutrient pounds supplied.
Fertilizer from nitrogen mode:
The calculator divides the target nitrogen amount by the fertilizer nitrogen percentage.
Fertilizer from phosphorus mode:
The calculator divides the target P₂O₅ amount by the fertilizer phosphorus percentage.
Fertilizer from potassium mode:
The calculator divides the target K₂O amount by the fertilizer potassium percentage.
An NPK calculator helps compare fertilizer labels and estimate how much nitrogen, phosphorus, and potassium a fertilizer application supplies.
It can help calculate fertilizer needed from a nutrient target, estimate bags to buy, compare product strength, plan seasonal applications, and estimate total fertilizer cost.
Your result shows estimated nitrogen, phosphorus, and potassium supplied, fertilizer amount needed, bags required, application cost, seasonal cost, nutrient rate per 1,000 square feet, and NPK ratio based on the fertilizer label.
NPK stands for nitrogen, phosphorus, and potassium. Fertilizer labels list these as percentages by weight.
Multiply the fertilizer amount by each NPK percentage as a decimal. For example, 10 pounds of 10-10-10 supplies about 1 pound of each listed nutrient.
Divide the target nitrogen pounds by the nitrogen percentage as a decimal. A 10% nitrogen fertilizer needs 10 pounds of fertilizer to supply 1 pound of nitrogen.
Most fertilizer labels list phosphorus as phosphate P₂O₅ and potassium as potash K₂O, not elemental P and K.
No. This is an estimate. Actual fertilizer needs vary by soil test results, crop type, fertilizer form, soil texture, irrigation, weather, and local growing conditions.