Fertilizer Calculator

N-P-K represents the percentage by weight of nitrogen (N), phosphorus (P₂O₅), and potassium (K₂O) in the fertilizer. For example, a 15-5-10 fertilizer contains 15% nitrogen, 5% phosphorus, and 10% potassium.

Application rates should be based on a recent soil test report, which will recommend specific amounts of each nutrient needed for your lawn type and soil conditions. Without a soil test, follow general guidelines for your grass type.

Yes, this calculator helps you determine how much of any available fertilizer to apply to meet your target nutrient rates. You may need to apply more or less depending on the N-P-K analysis of your available fertilizer.

A 3-1-2 ratio of N-P-K is generally recommended for established lawns (like 15-5-10). However, established lawns often don't need additional phosphorus, so nitrogen-only fertilizers may be appropriate if soil phosphorus levels are adequate.

Measure as accurately as possible since fertilizer application is calculated per square foot. For irregular shapes, break your lawn into rectangles, triangles, or circles and add the areas together for the most accurate calculation.

Over-fertilizing can burn your grass, promote excessive growth requiring more mowing, increase disease susceptibility, and contribute to environmental pollution through runoff. Always follow recommended application rates.

Timing depends on your grass type and location. Cool-season grasses typically benefit from spring and fall applications, while warm-season grasses are best fertilized during their active growing season in late spring and summer.

Most fertilizers should be watered in lightly after application to help dissolve the nutrients and prevent burning. Check the product label for specific watering instructions, as some slow-release fertilizers may have different requirements.