Biology

Fertilizer Calculator

Find fertilizer needed for a nitrogen rate.

Area

N rate (lb N/1000 ft²)

Fertilizer N (%)

Calculated Output

Fertilizer needed 5

Formula: lb = (rate × area/1000) ÷ (N% ÷ 100)

Step-by-Step Breakdown

1. Values used:

2. Area = 1,000

3. N rate = 1 lb N/1000 ft²

4. Fertilizer N = 20 %

6. Fertilizer needed = 5

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The math behind it

Pounds of N needed = rate × area ÷ 1000; divide by the fertilizer's N fraction (first number in N-P-K).

1,000 ft², 1 lb N/1000, 20-N fertilizer → 5 lb.

N-P-K?

The three numbers are the % of nitrogen, phosphorus and potassium.