Fertilizer Calculator
Applying the right amount of fertilizer keeps your lawn green and your garden productive without wasting money or polluting waterways. Enter your area, the N-P-K ratio on your bag, and how much nitrogen you want to apply per 1,000 square feet.
The three numbers on a fertilizer bag represent the percentage by weight of nitrogen (N), phosphorus (P), and potassium (K). A 10-10-10 bag is 10% nitrogen, 10% phosphorus, and 10% potassium. To figure out how much product to spread, divide the desired nitrogen rate by the nitrogen percentage.
For example, if you want 1 lb of nitrogen per 1,000 sq ft and your fertilizer is 10-10-10, you need 1 / 0.10 = 10 lb of product per 1,000 sq ft. Multiply that rate by your total area (in thousands of square feet) to get the total bag weight.
Most cool-season lawns do well with 2 to 4 lb of nitrogen per 1,000 sq ft per year, split across 2 to 4 applications. Warm-season grasses may need a bit more. Gardens vary widely by crop, so a soil test is always the best starting point. Over-fertilizing wastes money and can burn plants, and excess nutrients washing into storm drains contribute to algal blooms in lakes and rivers.