What do the numbers on a fertilizer bag mean?
The three numbers (for example 24-0-6) are the percentage by weight of nitrogen (N), phosphate (P₂O₅) and potash (K₂O). A 15 lb bag of 24-0-6 contains 3.6 lb of nitrogen.
How the calculation works
Lawn recommendations are usually given in pounds of nitrogen per 1,000 sq ft. To find the amount of product, divide the nitrogen target by the nitrogen percentage. Example: 1 lb N ÷ 0.24 = 4.2 lb of 24-0-6 per 1,000 sq ft.
How often should I fertilize?
Most lawns do well with 2–4 lb of nitrogen per 1,000 sq ft per year, split into several applications of about 1 lb or less. Cool-season lawns are fed mainly in fall, warm-season lawns during late spring and summer.
Follow the label and local rules
Always follow the product label. Some states and towns restrict phosphorus or limit fertilizing near water and before heavy rain. A soil test from your local extension office tells you exactly what your lawn needs.