Lawn fertilizer calculator
How much fertilizer to spread for one feeding, from your lawn size and the first number on the bag (its nitrogen).
How the math works
Lawn feeding rates are given in pounds of nitrogen per 1,000 sq ft. A bag labeled 24-0-6 is 24% nitrogen, so 1 lb of nitrogen takes 1 ÷ 0.24 = 4.2 lb of that fertilizer. For a 5,000 sq ft lawn that's 5 × 4.2 = 21 lb per feeding.
- Use 1 lb of nitrogen per 1,000 sq ft at most in one feeding; use 0.5 lb in summer heat or with fast-release fertilizer.
- Most lawns need 2–4 lb of nitrogen per 1,000 sq ft a year, split into several feedings. Centipede, bahia and fine fescue need less, about 1–2 lb.
- The middle and last numbers are phosphorus and potassium. Most established lawns need little phosphorus unless a soil test says so.
- The bag's spreader setting is for its own label rate; if you spread a different amount, adjust or make two lighter passes.
When to fertilize
Timing matters as much as the amount: cool-season lawns get most of their food in fall, warm-season lawns in late spring and summer. See the lawn fertilizer schedule, or check your ZIP code for this year's feeding windows where you live.
Seeding too? Try the grass seed calculator.