Fertilizer Calculator
Work out how much fertilizer to spread on your lawn. Enter the lawn area, the three N-P-K numbers on the bag and how many pounds of nitrogen (or phosphate or potash) per 1,000 sq ft you want, and get the pounds of product, bags and nutrients applied.
1 lb of N per 1,000 sq ft is a typical single feeding.
How to use the Fertilizer Calculator
- Enter your lawn area in square feet, or its length and width.
- Enter the N-P-K numbers printed on the fertilizer bag and the bag weight.
- Choose the nutrient and target rate, usually 0.5-1 lb of nitrogen per 1,000 sq ft per feeding.
- Add the bag price if you want a cost.
- Read the pounds of fertilizer and bags, then set your spreader to deliver that amount per 1,000 sq ft.
Fertilizer rate formula
Product per 1,000 sq ft = target nutrient (lb per 1,000 sq ft) ÷ (nutrient % ÷ 100)
Total product = product per 1,000 sq ft × lawn area ÷ 1,000
Example: a 5,000 sq ft lawn, 24-0-11 fertilizer, 1 lb of N per 1,000 sq ft: 1 ÷ 0.24 = 4.17 lb per 1,000 sq ft, × 5 = 20.8 lb of fertilizer, which also supplies 0.46 lb of K₂O per 1,000 sq ft. A 50 lb bag covers 12,000 sq ft at this rate.
Pounds of product for 1 lb of nitrogen per 1,000 sq ft
| Fertilizer (N-P-K) | Product per 1,000 sq ft | Coverage of a 50 lb bag |
|---|---|---|
| 46-0-0 (urea) | 2.17 lb | 23,000 sq ft |
| 32-0-4 | 3.13 lb | 16,000 sq ft |
| 29-0-4 | 3.45 lb | 14,500 sq ft |
| 24-0-11 | 4.17 lb | 12,000 sq ft |
| 21-0-0 (ammonium sulfate) | 4.76 lb | 10,500 sq ft |
| 18-24-12 (starter) | 5.56 lb | 9,000 sq ft |
| 16-4-8 | 6.25 lb | 8,000 sq ft |
| 10-10-10 | 10 lb | 5,000 sq ft |
| 5-3-4 (organic) | 20 lb | 2,500 sq ft |
Phosphate and potash on the label are reported as P₂O₅ and K₂O, as used in soil test recommendations. Some areas restrict phosphorus on lawns; check local rules and use a soil test to decide what your lawn actually needs.
Frequently asked questions
How do I calculate how much fertilizer to use?
Divide the pounds of nutrient you want per 1,000 sq ft by the nutrient percentage as a decimal. For 1 lb of nitrogen with a 24-0-11 fertilizer: 1 ÷ 0.24 = 4.17 lb of product per 1,000 sq ft. Multiply by your lawn area in thousands of square feet for the total.
What do the three numbers on fertilizer mean?
N-P-K are the percentages by weight of nitrogen (N), phosphate (P₂O₅) and potash (K₂O). A 50 lb bag of 10-10-10 contains 5 lb each of N, P₂O₅ and K₂O; the rest is filler and other ingredients.
How much nitrogen does a lawn need?
Many cool-season and warm-season lawns get 2 to 4 lb of nitrogen per 1,000 sq ft per year, split into several feedings of 0.5 to 1 lb. Exact needs depend on grass type, climate, soil and whether clippings are left on the lawn; a soil test and local extension advice are the best guide.
How much area does a 50 lb bag of fertilizer cover?
It depends on the nitrogen content and the rate. At 1 lb N per 1,000 sq ft, a 50 lb bag of 24-0-11 covers 50 ÷ 4.17 × 1,000 = 12,000 sq ft, while a 50 lb bag of 10-10-10 covers only 5,000 sq ft.
Can I put down too much fertilizer?
Yes. Too much quick-release nitrogen at once can burn grass, and excess nutrients wash into streams and lakes. Stay at or below about 1 lb of soluble nitrogen per 1,000 sq ft per application and follow local fertilizer rules.
How do I calculate my lawn area?
Measure the length and width of each rectangular section in feet and multiply. Subtract the house, driveway and beds. 1 acre is 43,560 sq ft.