Fertilizer Calculator — How Much Fertilizer Do I Need?
Calculate the amount of fertilizer needed for any field area based on target application rate.
Quick Select
Product / Acre
260.9 lb
Total Product (lb)
1304.3 lb
Total Product (tons)
0.65 tons
Formula
**Fertilizer Application Rate Formula**
Product lbs/Acre = Target Nutrient lbs/Acre ÷ (Nutrient % ÷ 100)
Total Product = Product lbs/Acre × Total Acres
Common: Urea (46-0-0): 46% N | Ammonium Nitrate (34-0-0): 34% N | Potash (0-0-60): 60% K₂O
Worked Example
**Example:** 5 acres, 120 lb N/acre, urea (46% N)
Product/Acre = 120 ÷ 0.46 = **260.9 lb/acre**
Total = 260.9 × 5 = **1,304.3 lb = 0.65 tons**
Frequently Asked Questions
What do the three numbers on fertilizer bags mean?
N-P-K: Nitrogen (%), Phosphorus as P₂O₅ (%), Potassium as K₂O (%). A 10-10-10 bag contains 10% of each nutrient by weight.
How do I know my target application rate?
A soil test from your county extension service provides a recommendation in lbs of actual nutrient per acre.
How many bags do I need?
Divide total product lbs by the bag size (most granular fertilizers come in 50 lb bags) and round up.