Lawn Fertilizer Calculator
Calculate pounds of fertilizer product to apply a target rate of nitrogen.
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What this tool does
This calculator converts a nitrogen target (typically 0.5–1 lb N per 1,000 sq ft per feeding) and the N percentage on your fertilizer bag into the pounds of product to spread over your lawn.
How to use the Lawn Fertilizer Calculator
- Enter your lawn area.
- Enter the first number of the N-P-K analysis on the bag.
- Enter your nitrogen target per 1,000 sq ft.
- Enter the bag weight.
- Set your spreader to the product rate per 1,000 sq ft.
Formula
Product per 1,000 = N_target ÷ (N% ÷ 100); Total = per 1,000 × Area ÷ 1,000
- N_target
- lb of nitrogen per 1,000 sq ft
- N%
- Nitrogen percent on bag
- Area
- Lawn sq ft
Worked example
5,000 sq ft fed with 24-0-6 at 1 lb N per 1,000 sq ft.
Inputs
- Lawn area5000 sq ft
- Nitrogen % (first number on bag)24 %
- Target N per 1,000 sq ft1 lb
- Bag weight12 lb
Result
- Fertilizer needed20.83 lb
- Product per 1,000 sq ft4.17 lb
- Bags2
- Actual nitrogen applied5 lb
Product needed for 1 lb N / 1,000 sq ft
| Bag analysis | lb product / 1,000 sq ft |
|---|---|
| 10-x-x | 10.00 |
| 16-x-x | 6.25 |
| 20-x-x | 5.00 |
| 24-x-x | 4.17 |
| 29-x-x | 3.45 |
| 32-x-x | 3.13 |
| 46-x-x | 2.17 |
Results explained
- Fertilizer needed
- Pounds of product for the whole lawn.
- Per 1,000 sq ft
- Spreader rate.
- Bags
- Whole bags.
- Actual N
- Pounds of nitrogen you'll apply.
Frequently asked questions
Cool-season lawns usually need 2–4 lb N per 1,000 sq ft per year, split into several feedings.
Percent by weight of nitrogen, phosphate (P₂O₅) and potash (K₂O).
10 lb of 10-10-10 delivers 1 lb of nitrogen per 1,000 sq ft.
Yes — more than about 1 lb of quick-release N per feeding can burn grass and leach into waterways.
Mainly in early and late fall, with a lighter feeding in late spring.