A 5,000 sq ft lawn at a label rate of 3.2 lb per 1,000 sq ft needs 16 lb of fertilizer — one 40 lb bag with plenty left over. The rate on your bag decides everything, so enter it in the free QtyLab fertilizer calculator.
Below: the formula, how to get a rate from the N-P-K numbers, a chart by lawn size, and a shopping list.
The fertilizer formula
- Pounds of product = (lawn area ÷ 1,000) × rate in lb per 1,000 sq ft
- Bags = pounds ÷ bag size, rounded up
Worked example: 5,000 sq ft at 3.2 lb/1,000 sq ft → 5 × 3.2 = 16 lb. A 40 lb bag covers it.
No rate on the bag? Use the nitrogen number
The first of the three numbers on the bag (like 29-0-4) is the percent nitrogen. Many extension guides work from pounds of nitrogen per 1,000 sq ft; a common single application is about 1 lb. To convert:
- Pounds of product per 1,000 sq ft = pounds of nitrogen wanted ÷ (nitrogen % ÷ 100)
| Bag nitrogen % | Product for 0.5 lb N / 1,000 sq ft | Product for 1 lb N / 1,000 sq ft |
|---|---|---|
| 10% | 5.0 lb | 10.0 lb |
| 16% | 3.1 lb | 6.3 lb |
| 20% | 2.5 lb | 5.0 lb |
| 25% | 2.0 lb | 4.0 lb |
| 29% | 1.7 lb | 3.4 lb |
| 32% | 1.6 lb | 3.1 lb |
The label on your product wins over any chart, including this one. Your grass type, season, and local rules may call for less.
Chart by lawn size
Pounds of product. Click a row to open it in the calculator.
| Lawn area | At 3.2 lb / 1,000 sq ft | At 3.45 lb / 1,000 sq ft (1 lb N from 29% N) |
|---|---|---|
| 2,000 sq ft | 6.4 lb | 6.9 lb |
| 5,000 sq ft | 16.0 lb | 17.3 lb |
| 10,000 sq ft | 32.0 lb | 34.5 lb |
| Half acre (21,780 sq ft) | 69.7 lb | 75.1 lb |
| 1 acre (43,560 sq ft) | 139.4 lb | 150.3 lb |
How much does one bag cover?
Coverage = bag weight ÷ rate × 1,000. At 3.2 lb per 1,000 sq ft, a 40 lb bag covers 12,500 sq ft and a 15 lb bag covers about 4,700 sq ft. Many bags also print “covers X sq ft” on the front — use that number with your spreader setting.
Common mistakes
- Guessing the lawn size. Measure it; the house and driveway are not lawn.
- Mixing up product pounds and nitrogen pounds. “1 lb of nitrogen” can mean 3 to 10 lb of product.
- Doubling up to be safe. Over-applying can burn grass. Follow the label.
- Skipping the spreader setting. The bag lists settings for common spreaders — use them.
Shopping list for a 5,000 sq ft lawn
- About 16 lb of lawn fertilizer at a 3.2 lb/1,000 rate — one bag labeled for at least 5,000 sq ft — shop lawn fertilizer
- 1 broadcast spreader — shop broadcast spreaders
- 1 handheld spreader for small or narrow areas, optional — shop handheld spreaders
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Laying new sod? See how much sod you need.
Fertilizer FAQ
How much fertilizer do I need for 1,000 square feet?
Use the rate on your bag, in pounds per 1,000 sq ft. Many lawn products fall around 3 to 4 lb of product per 1,000 sq ft. For a 29% nitrogen product, about 3.4 lb delivers 1 lb of nitrogen.
How many square feet does a 40 lb bag of fertilizer cover?
At 3.2 lb per 1,000 sq ft, a 40 lb bag covers 12,500 sq ft. At a lower rate it covers more; at a higher rate, less. Check the coverage printed on the bag.
How do I convert nitrogen to pounds of fertilizer?
Divide the pounds of nitrogen you want by the nitrogen percentage as a decimal. Example: 1 lb of nitrogen from a 25% product is 1 ÷ 0.25 = 4 lb of product per 1,000 sq ft.
How much fertilizer do I need for an acre?
An acre is 43,560 sq ft. At 3.2 lb per 1,000 sq ft, that is about 139 lb of product.
Should I round up to full bags?
Yes. Buy whole bags, apply only the label rate, and store the rest dry and sealed as the label directs.
Nitrogen conversion method: Rutgers NJAES FS839.