Lawn Fertilizer Calculator
Enter your lawn area, the N-P-K on the bag and the nitrogen rate you want per 1,000 sq ft. You get the pounds of product to spread, what one bag covers at that rate, and the annual plan for your grass type.
The three numbers on the bag, e.g. 24-0-6.
1 lb is the standard single application; 0.5 for slow, light feeding; never over 1 with quick-release.
Fertilizer to apply
20.8 lb
1.30 bags of 16 lb
Per 1,000 sq ft
4.2 lb
the spreader setting target
One bag covers
3,840 sq ft
at 1 lb N
Also delivers
0.0 lb P₂O₅ · 1.3 lb K₂O
phosphate and potash
| Tall fescue annual plan | lb N per 1,000 sq ft / yr | Applications | Bags of this product / yr |
|---|---|---|---|
| Low-maintenance | 2 | 2 × 1 lb | 2.6 |
| High-maintenance | 3 | 3 × 1 lb | 3.9 |
lb of product = lb N wanted ÷ (N% ÷ 100). A 24-0-6 bag is 24% nitrogen by weight, so 4.2 lb of it carries 1 lb of N.
Product per 1,000 sq ft for 1 lb of nitrogen
| Analysis | lb per 1,000 sq ft | For 5,000 sq ft | For 10,000 sq ft | A 16 lb bag covers |
|---|---|---|---|---|
| 10-10-10 | 10.0 | 50.0 | 100.0 | 1,600 sq ft |
| 16-4-8 | 6.3 | 31.3 | 62.5 | 2,560 sq ft |
| 24-0-6 | 4.2 | 20.8 | 41.7 | 3,840 sq ft |
| 29-0-4 | 3.4 | 17.2 | 34.5 | 4,640 sq ft |
| 32-0-4 | 3.1 | 15.6 | 31.3 | 5,120 sq ft |
| 46-0-0 (urea) | 2.2 | 10.9 | 21.7 | 7,360 sq ft |
| 21-0-0 (ammonium sulfate) | 4.8 | 23.8 | 47.6 | 3,360 sq ft |
Annual nitrogen by grass type
| Grass | lb N / 1,000 sq ft / yr | Applications | Timing |
|---|---|---|---|
| Kentucky bluegrass | 3–4 | 4 | Sept, Oct/Nov heaviest; light in May; none in summer |
| Tall fescue | 2–3 | 3 | Sept, Oct/Nov heaviest; light in May; none in summer |
| Perennial ryegrass | 2–3 | 3 | Sept, Oct/Nov heaviest; light in May; none in summer |
| Fine fescue | 1–2 | 2 | Sept, Oct/Nov heaviest; light in May; none in summer |
| Bermuda | 4–5 | 5 | May through August, once soil is warm; none after early fall |
| Zoysia | 2–3 | 3 | May through August, once soil is warm; none after early fall |
| St. Augustine | 3–4 | 4 | May through August, once soil is warm; none after early fall |
| Centipede | 1–2 | 2 | May through August, once soil is warm; none after early fall |
Slow release, quick release, and burn
- Quick-release nitrogen (urea, ammonium sulfate) greens in days and is gone in weeks. Never more than 1 lb N per application, and water it in; it burns.
- Slow-release (polymer-coated urea, methylene urea, organics) feeds over 8-12 weeks and can go on at 1-1.5 lb. The bag lists the slow-release share as "% slowly available nitrogen".
- Do not apply to dormant or drought-stressed grass, or before heavy rain: the nitrogen runs off and the lawn does not use it.
- A soil test every two or three years tells you whether P and K are needed at all; most established lawns need nitrogen only.
Frequently Asked Questions
How much fertilizer do I need for my lawn?
Decide the nitrogen rate -- 1 lb of actual N per 1,000 sq ft is the standard application -- then divide by the bag's N percentage. A 24-0-6 bag is 24% nitrogen, so 4.17 lb of product delivers 1 lb of N; for 5,000 sq ft that is 20.8 lb. A 16 lb bag of 24-0-6 covers 3,840 sq ft at that rate, whatever the bag claims.
What do the three numbers mean?
N-P-K: percent nitrogen, percent phosphate (P₂O₅) and percent potash (K₂O) by weight. 24-0-6 is 24% N, 0% phosphate, 6% potash; the rest is filler and carrier. Nitrogen drives colour and growth and is the number lawns are dosed by. Phosphorus is banned or restricted for established lawns in many states; potassium helps stress tolerance.
How much nitrogen per year?
By grass, from extension guidance: Kentucky bluegrass 3-4 lb N per 1,000 sq ft a year, tall fescue 2-3, fine fescue 1-2, bermuda 4-5, zoysia 2-3, St. Augustine 3-4, centipede 1-2. Split it into applications of 0.5-1 lb, timed to the growing season: fall-heavy for cool-season grasses, summer for warm-season.
Why not follow the bag's coverage claim?
Bag coverage assumes the manufacturer's chosen rate, which is often 0.75 lb N or less to make the bag look bigger, and sometimes over 1 lb for a 'fast greening' product. Working from N percentage and your chosen rate makes every bag comparable and stops both over- and under-feeding.
What spreader setting do I use?
The setting on the bag is a starting guess for that spreader. Calibrate: weigh out the product for a known area (say 1,000 sq ft), spread it at the bag setting, and see what is left. Adjust and repeat. Applying half the total in each of two directions evens out any error.
These calculators use published seeding rates, extension-service fertilizer guidance, and standard pool-chemistry dosing figures, and are for planning. Read the product label; it governs the dose. Pool chemicals are hazardous when mixed or mishandled, and a pool store's water test beats any estimate here.