YardHow to use the fertilizer calculator
Calculate fertilizer
Never exceed about 1 lb of nitrogen per 1,000 sq ft in a single application. Follow your product label and local rules, and sweep granules off paths and driveways. Estimates only.
- Choose the shape of your lawn: rectangle, circle or triangle.
- Enter the length and width (or diameter) in feet. Measure only the lawn, not paths, beds or the house.
- Enter the product rate from your bag, in pounds per 1,000 sq ft. Most lawn fertilizers are applied at 3 to 4 lb per 1,000 sq ft. Add the nitrogen percentage (the first of the three N-P-K numbers) if you want the nitrogen total.
- Read off the product needed, the bags to buy and the nitrogen you are applying.
Read the bag: the N-P-K numbers
Every fertilizer bag shows three numbers, like 24-0-6. They are the percentages by weight of nitrogen (N), phosphorus (P) and potassium (K). A 50 lb bag of 24-0-6 holds 12 lb of actual nitrogen. Nitrogen drives green growth, phosphorus supports roots (and is restricted near waterways in many states), and potassium helps stress tolerance. A soil test every couple of years tells you which of these your lawn actually needs instead of guessing.
The one-pound rule
Lawn advice is usually given in pounds of nitrogen, not product. The safe standard is about 1 lb of nitrogen per 1,000 sq ft per application at most, with cool-season lawns totalling roughly 2 to 4 lb per year spread over two to four feedings. This calculator works in product weight because that is what you weigh out, and it shows the nitrogen total as well so you can check it against the rule. To hit exactly 1 lb of nitrogen with a 24 percent product, you would apply about 4.2 lb of product per 1,000 sq ft.
Typical application rates
| Product type | Rate (lb per 1,000 sq ft) | Nitrogen delivered |
|---|---|---|
| Standard lawn fertilizer (24% N) | 3.5 | About 0.84 lb N |
| High-nitrogen lawn food (32% N) | 3.0 | About 0.96 lb N |
| Starter fertilizer (18% N) | 4.0 | About 0.72 lb N |
| Organic lawn food (6% N) | 10–15 | About 0.6–0.9 lb N |
| Winterizer (28% N) | 3.5 | About 0.98 lb N |
Tips for applying fertilizer
- A soil test beats guesswork: many lawns need nitrogen only, and adding phosphorus you do not need wastes money and can break local rules near lakes and streams.
- Sweep granules off paths and driveways back onto the lawn so they do not wash into drains.
- Water lightly after applying granular fertilizer (unless the label says otherwise) and never apply right before heavy rain.
- Calibrate your spreader on a driveway section, and apply half the product in each of two crossing passes for even coverage, the same trick as seeding.