Fertilizer Calculator

sq ft
lbs N / 1000 sq ft
Typical: 1 lb N/1000 sq ft per application.
%
First number in the NPK ratio (e.g., 20 for 20-5-10).
Biology

Calculate how many pounds of fertilizer to apply based on lawn area, desired nitrogen rate, and fertilizer NPK content.

Formula

Fertilizer (lbs) = (Area ÷ 1000) × (N rate ÷ N fraction)
  • N rate is typically 0.5–1.5 lbs per 1,000 sq ft per application.
  • N fraction = first NPK number ÷ 100 (e.g., 20% N → 0.20).
  • Apply no more than 1 lb N/1000 sq ft per application to avoid burn.

1000 sq ft, 1 lb N rate, 20% N fertilizer

Inputs
  • Lawn Area: 1000 sq ft
  • Desired Nitrogen Rate: 1 lbs N / 1000 sq ft
  • Fertilizer N Content: 20 %

1 lb N needed. 20% N product: 1 ÷ 0.20 = 5 lbs fertilizer per 1,000 sq ft.

Frequently asked questions

What does NPK stand for?
Nitrogen (N), Phosphorus (P), Potassium (K) — the three primary macronutrients.
When is the best time to fertilize?
Cool-season grasses: fall and spring. Warm-season grasses: late spring to summer.