Fertilizer Calculator
Turn the N-P-K numbers on any bag into how much to spread per 1,000 sq ft and for your whole lawn, by nitrogen or by a soil test's phosphate or potash, with feeding times for your grass.
Pounds of fertilizer per 1,000 sq ft = pounds of nutrient wanted ÷ (percent on the bag ÷ 100). For 1 lb of nitrogen with 24-0-6: 1 ÷ 0.24 = 4.2 lb per 1,000 sq ft, or 20.8 lb for a 5,000 sq ft lawn. With 10-10-10 it takes 10 lb per 1,000 sq ft. Most lawns need 1–4 lb of nitrogen per 1,000 sq ft a year, split into feedings of about 1 lb.
Fertilizer for 1 lb of nitrogen per 1,000 sq ft
| Product (N-P-K) | Per 1,000 sq ft | 50 lb bag covers |
|---|---|---|
| 24-0-6 | 4.2 lb | 12,000 sq ft |
| 32-0-4 | 3.1 lb | 16,000 sq ft |
| 29-0-4 | 3.4 lb | 14,500 sq ft |
| 16-4-8 | 6.3 lb | 8,000 sq ft |
| 10-10-10 | 10.0 lb | 5,000 sq ft |
| 15-0-15 | 6.7 lb | 7,500 sq ft |
| 46-0-0 | 2.2 lb | 23,000 sq ft |
| 21-0-0 | 4.8 lb | 10,500 sq ft |
| 5-3-2 | 20.0 lb | 2,500 sq ft |
| 28-0-0 | 3.6 lb | 14,000 sq ft |
Yearly nitrogen by grass type
| Grass | Season | Lb N per 1,000 sq ft per year |
|---|---|---|
| Kentucky bluegrass | Cool-season | 2–4 |
| Tall fescue | Cool-season | 2–4 |
| Perennial ryegrass | Cool-season | 2–4 |
| Fine fescue | Cool-season | 1–2 |
| Bermudagrass | Warm-season | 2–5 |
| Zoysiagrass | Warm-season | 1–3 |
| St. Augustinegrass | Warm-season | 2–4 |
| Centipedegrass | Warm-season | 1–2 |
| Buffalograss | Warm-season | 1–2 |
Frequently asked questions
How do I calculate how much fertilizer to use?
Decide how much nitrogen you want per 1,000 sq ft (usually 0.5–1 lb), divide by the first number on the bag as a decimal, and multiply by your lawn area in thousands of square feet. 1 lb N with 32-0-4 is 1 ÷ 0.32 = 3.1 lb per 1,000 sq ft.
What do the three numbers on fertilizer mean?
They are the percent by weight of nitrogen (N), phosphate (P₂O₅) and potash (K₂O). A 50 lb bag of 10-10-10 contains 5 lb of each.
How much 10-10-10 per 1,000 square feet?
10 lb per 1,000 sq ft for 1 lb of nitrogen, or 5 lb for a half-rate feeding.
How often should I fertilize my lawn?
Cool-season grasses mostly in fall (2–3 feedings), warm-season grasses every 6–8 weeks from green-up through summer. Your grass type sets the yearly total.
Can I put down too much fertilizer?
Yes. More than about 1 lb of quick-release nitrogen per 1,000 sq ft at once can burn the lawn, and excess nutrients wash into waterways. Split heavy rates and follow the label.
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Product rate = nutrient rate ÷ (grade % ÷ 100); N-P-K grades are percent by weight of N, P₂O₅ and K₂O. Yearly nitrogen ranges reflect university extension guidance such as Purdue Turfgrass Science and NC State TurfFiles; your state's extension service and a soil test give the best numbers for your lawn. Liquid rates use the product's weight per gallon from its label.