Fertilizer Calculator

Those are the N-P-K ratio: percent nitrogen (N), phosphate (P2O5), and potash (K2O) by weight. A 50 lb bag of 10-10-10 contains 5 lb of N, 5 lb of P2O5, and 5 lb of K2O. The rest is filler and minor nutrients.

One pound of actual nitrogen per 1,000 sq ft is a common planning rate, not a universal prescription. For a 5,000 sq ft lawn with 25-0-10 fertilizer, 5 lb of N divided by 25% equals 20 lb of product. The calculator handles the math for any N-P-K and rate. Follow the label, a soil test, and local extension or nutrient rules.

Choose fertilizer from a soil test, grass species, season, and local rules rather than a universal N-P-K ratio. Established turf often needs no added phosphorus, and many jurisdictions restrict it. New seed or sod may need a starter product only when the label and local extension guidance support it.

Cool-season: 2-4 applications between September and May; skip mid-summer. Warm-season: 3-5 applications May through September. Avoid late-fall N on warm-season grass (encourages disease). Slow-release blends spread out the feeding.

Yes. Too much nitrogen burns leaves, causes thatch buildup, and pollutes runoff. Stay below 1 lb of N per 1,000 sq ft per application, and never apply right before heavy rain. Water-in granular fertilizer immediately to prevent burn.