Lawn Fertilizer Calculator (NPK)
By NPK Ratio
Calculate fertilizer amount based on your product's NPK ratio
By Grass Type
Get annual fertilizer recommendations by grass type
Formula
Fertilizer (lbs) = (Area / 1000 × N Rate) / (N% / 100) | Application Rate = Fertilizer Needed / (Area / 1000)
Frequently Asked Questions
What does NPK mean on fertilizer?
NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K). A 20-5-10 fertilizer contains 20% nitrogen, 5% phosphorus, and 10% potassium by weight. Nitrogen promotes green growth, phosphorus supports roots, and potassium improves overall plant health.
How much fertilizer should I put on my lawn?
Apply 1 lb of actual nitrogen per 1,000 sq ft per application. With a 20-5-10 fertilizer, that is 5 lbs of product per 1,000 sq ft. Apply 3-4 times per year for cool-season grasses, 4-5 times for warm-season grasses.
When should I fertilize my lawn?
Cool-season grasses (fescue, bluegrass): September is the most important feeding, with a second in late spring. Warm-season grasses (bermuda, zoysia): Feed from late spring through late summer when grass is actively growing. Never fertilize frozen or dormant lawns.
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