Fertilizer Rate Calculator
Enter your fertilizer's N–P–K analysis, your target pounds of nitrogen per 1,000 sq ft, and the lawn's square footage. The calculator returns the exact bag rate, total product needed, and bags to buy.
How this fertilizer rate calculator works
Fertilizer is sold by analysis, not by how much nitrogen your lawn actually needs — so every bag requires a quick conversion. The first number in the N–P–K analysis is the percentage of nitrogen by weight. A 46-0-0 bag is 46% nitrogen; a 24-0-6 bag is 24%. To put down your target pounds of nitrogen per 1,000 sq ft, you divide that target by the nitrogen percentage to get the pounds of product per 1,000.
For example, to apply 1 lb of nitrogen per 1,000 sq ft using a 24-0-6 fertilizer, you need about 4.2 lbs of product per 1,000 sq ft (1 ÷ 0.24). On a 5,000 sq ft lawn that's roughly 21 lbs of product. This calculator runs that math for you and rounds up to whole bags so you know exactly what to buy.
Most cool-season lawns want about 0.5 to 1 lb of nitrogen per 1,000 sq ft per application, and 2 to 4 lbs total per year depending on the grass and your goals. Lean on slow-release nitrogen during heat and never exceed the product label's maximum single-application rate.
Frequently asked questions
How do I convert N–P–K to pounds of fertilizer per 1,000 sq ft?
Divide your target pounds of nitrogen per 1,000 sq ft by the nitrogen percentage (the first N–P–K number, as a decimal). To put down 1 lb of N with a 24-0-6 product: 1 ÷ 0.24 ≈ 4.2 lbs of product per 1,000 sq ft.
How much nitrogen does a lawn need?
Most cool-season lawns want 0.5–1 lb of nitrogen per 1,000 sq ft per application and 2–4 lbs per year total. Warm-season grasses and your specific goals shift that range, so confirm with the product label and local guidance.
What do the three N–P–K numbers mean?
They're the percentages by weight of nitrogen (N), phosphorus (P), and potassium (K). A 24-0-6 bag is 24% nitrogen, 0% phosphorus, and 6% potassium; the rest is filler and carrier.
Can I apply too much fertilizer?
Yes — over-applying nitrogen can burn the lawn, push weak surge growth, and run off into waterways. Always stay within the product label's maximum single-application and annual rates.
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