How to calculate lawn fertilizer
Lawn feeding is planned around nitrogen, the first number in the N-P-K ratio on the bag. A 24-0-6 fertilizer is 24% nitrogen by weight.
Total = Lawn area ÷ 1,000 × Fertilizer per 1,000 sq ft
Worked example
A 5,000 sq ft lawn, 24-0-6 fertilizer, aiming for 1 lb of nitrogen per 1,000 sq ft: 1 ÷ 0.24 = 4.17 lb per 1,000 sq ft. For 5,000 sq ft that's 20.8 lb, a little more than one 15 lb bag.
Reading N-P-K
| Letter | Nutrient | What it does |
|---|---|---|
| N | Nitrogen | Green color and leaf growth |
| P | Phosphorus | Roots, mainly for new lawns |
| K | Potassium | Drought, heat and disease tolerance |
How much nitrogen per year?
Most lawns need 2–4 lb of nitrogen per 1,000 sq ft per year, split into applications of 0.5–1 lb. Cool-season grasses are fed mainly in fall, and warm-season grasses in late spring and summer. Many US states limit phosphorus in lawn fertilizer, and some limit application timing, so check your local rules.
Tips
- Don't spread before heavy rain, and sweep granules off driveways and sidewalks so they don't wash into drains.
- Set your spreader using the setting on the bag, then check it covers the area you expect.
- A soil test tells you which nutrients your lawn actually needs.
Frequently asked questions
How much fertilizer do I need for 1,000 square feet?
To apply 1 lb of nitrogen with a 24% N product, you need about 4.2 lb of fertilizer per 1,000 sq ft. With a 10% N product, you need 10 lb.
What does 10-10-10 mean?
The bag is 10% nitrogen, 10% phosphorus (as P₂O₅) and 10% potassium (as K₂O) by weight. The other 70% is filler and carrier.
How often should I fertilize my lawn?
Typically 2–4 times a year, about 6–8 weeks apart, depending on grass type and whether you use slow-release fertilizer.
Last reviewed 2026-11-14. Material weights are typical industry averages and vary by supplier, moisture and compaction.