How to use this lawn fertilizer calculator
- Measure the lawn area.
- Choose a nitrogen rate: 0.5–1 lb N per 1,000 sq ft per application is typical.
- Read the N-P-K on the bag, e.g. 24-0-6, and enter the first number.
- Set your spreader so the calculated amount covers the whole area.
Example
A 4,000 sq ft lawn with a 30-0-4 fertilizer at 1 lb of nitrogen per 1,000 sq ft needs 13.3 lb of product (3.3 lb per 1,000 sq ft).
What to know before you buy
Reading a fertilizer label
The three numbers are N-P-K: nitrogen for green growth, phosphorus for roots and potassium for overall health. A 24-0-6 bag contains 24% nitrogen, no phosphorus and 6% potash. Many regions restrict phosphorus on lawns, so zero-phosphorus products are common.
How much nitrogen per year
Most lawns need 2–4 lb of nitrogen per 1,000 sq ft per year, split into several applications of 0.5–1 lb. Low-maintenance grasses need less; heavily used lawns in long growing seasons need more.
Fertilizer per 1,000 sq ft for 1 lb of nitrogen
| Fertilizer (N-P-K) | Fertilizer to apply |
|---|---|
| 10-10-10 | 10 lb |
| 16-4-8 | 6.2 lb |
| 24-0-6 | 4.2 lb |
| 29-0-4 | 3.4 lb |
| 32-0-4 | 3.1 lb |
| 46-0-0 (urea) | 2.2 lb |
Formula
Fertilizer (lb) = area ÷ 1,000 × nitrogen rate ÷ (N% ÷ 100).
Tips from the pros
- Apply fertilizer to dry grass and water it in, unless the label says otherwise.
- Use slow-release nitrogen for longer, more even feeding.
- Keep fertilizer off sidewalks and driveways, where it washes into storm drains.
Common mistakes to avoid
- Applying more nitrogen than needed, which burns grass and encourages disease.
- Fertilizing cool-season grass in the heat of summer.
Frequently asked questions
What do the numbers on fertilizer mean?
They are the percentages by weight of nitrogen (N), phosphate (P₂O₅) and potash (K₂O).
How often should I fertilize?
Cool-season lawns mainly in fall and spring; warm-season lawns in late spring and summer. Follow local extension advice.
How much fertilizer for 5,000 square feet?
For 1 lb of nitrogen per 1,000 sq ft with a 24% N product, about 21 lb.
Should I water after fertilizing?
For most granular fertilizers, yes: about 1/4 inch of water moves the nutrients into the soil.