Biology
Turn a nutrient rate into the amount of fertilizer product to apply.
Your inputs
Change any value — everything updates instantly.
The nutrient amount you want to apply, e.g. 2 lb of nitrogen.
The first number on the bag for nitrogen (urea is 46-0-0).
Try an example
Fertilizer to apply
4.35 lb
This means you spread about 4.35 lb (1.97 kg) of product.
What you are seeing
The bar is the product you weigh out.
Only the green 46% is the nutrient you want.
4.35 lb of product delivers 2 lb of nutrient.
Kilograms
1.97 kg
Same amount in kg.
Per 1 lb nutrient
2.17 lb
Product per pound of nutrient.
Nutrient share
46 %
From the bag analysis.
Result explanation: Product to weigh out
4.35 lb of a 46% product.
Real-life comparison: A 23% product would need 8.7 lb.
Low, normal or high? Weaker products need more weight for the same nutrient.
Product needed against analysis
How to read this chart: Stronger products need less weight. The red dot is your product.
Divides the nutrient you want by the fraction of it in the product.
4.35 lb of product.
Check which nutrient the percentage refers to (N, P₂O₅ or K₂O).
Split large applications into several smaller ones.
Nutrient wanted divided by the fraction in the bag.
product = nutrient needed ÷ (analysis % ÷ 100)
Symbols
Why this formula works
Only the stated fraction of the product is the nutrient.
Unit check
lb ÷ (%) = lb ✓
Worked example
Common mistakes
Apply 4.35 lb of product.
N – P₂O₅ – K₂O percentages by weight, in that order.
The one matching the nutrient you want to apply — first for nitrogen.
Same maths, but their analyses are lower and release is slower.
Yes — first work out nutrient per area, then divide by the analysis.
Reviewed 2026-09-25 · Next review 2027-09-25
Important limitation. Follow soil-test recommendations for actual nutrient needs.
Tell us if a formula, unit, explanation, or result needs attention. Your message will include this calculator’s name and page.
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