Free fertilizer application rate calculator. Get the exact product to apply from N-P-K targets, analysis and area — in lb/acre, lb/1,000 ft² or kg/ha.
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Applying the right amount of fertilizer is critical for healthy growth, strong yields, and protecting water quality. This calculator converts a soil-test recommendation into exactly how much product to apply — for row crops, lawns, or gardens — from the fertilizer's N-P-K analysis.
Fertilizer products list their nutrient content as N-P₂O₅-K₂O percentages (e.g., 10-10-10). To meet a recommendation like 100 lb N/acre, divide the target by the decimal analysis: 100 ÷ 0.46 = 217 lb of urea (46-0-0). This is the standard university-extension method (Virginia Tech VCE 424-035, Penn State, Iowa State).
Product Rate Formula
Convert a corn or wheat N recommendation into pounds of urea or ammonium nitrate per acre.
Size DAP, MAP, or potash to hit P₂O₅ and K₂O targets without guesswork.
Turn a per-1,000-sq-ft nitrogen rate into the exact amount of product to spread.
See what a blend like 10-10-10 delivers — and which nutrients it over- or under-applies.
Deliver exactly the nutrients your soil test recommends for maximum yield.
Avoid over-application that wastes money and harms the environment.
Prevent nutrient runoff by applying only what crops can use.
Fertilizer labels show phosphorus as P₂O₅ (phosphate), not elemental P. To convert P₂O₅ to P, multiply by 0.44 (and K₂O to K by 0.83). Soil tests usually recommend P₂O₅, matching fertilizer labels — this calculator also shows the elemental equivalent.
That's common. Base the rate on one nutrient (usually nitrogen), then read the balance: any nutrient shown as Short should be supplemented with a straight material, and any shown Over-applied means you'd waste it — pick a grade closer to your target ratio.
Multiply lbs/acre by 1.12 to get kg/ha. Or just switch the area unit to hectares and the calculator reports the rate in kg/ha automatically.
Lawns are dosed per 1,000 sq ft. Set the area unit to ft², enter your lawn's size, and use a nitrogen rate of about 0.5–1 lb N per 1,000 sq ft per application. The calculator converts that to product — e.g., 1 lb N ÷ 0.46 = 2.2 lb of urea per 1,000 sq ft.
Split applications are often more efficient, especially for corn and turf. Apply part at planting or green-up and the rest as a side-dress. Follow your local extension's split-application guidance.