Seed & feed
Grass seed & fertiliser calculator
Measure the lawn once, then get the seed for your grass type and the fertiliser that delivers the nitrogen you want, from the numbers on the bag.
Lawn of 1,500 sq ft.
Grass seedSchedule A
- Seed to sow10.5lb4.76 kg at 7 lb per 1,000 sq ft
- Extension range9–12lb6–8 lb per 1,000 sq ft
| Bag | Bags | One bag sows |
|---|---|---|
| 3 lb | 4 | 429 sq ft |
| 5 lb | 3 | 714 sq ft |
| 7 lb | 2 | 1,000 sq ft |
| 10 lb | 2 | 1,429 sq ft |
| 20 lb | 1 | 2,857 sq ft |
| 50 lb | 1 | 7,143 sq ft |
- Tall fescue, new lawn: 6–8 lb per 1,000 sq ft (29–39 g/m²), from Penn State Extension. The rate printed on your seed bag comes first.
FertiliserSchedule B
- 24-0-6 per 1,000 sq ft4.17lb= 20.3 g/m²
- For this lawn6.25lb2.83 kg
- Bags of 15 lb1bagone bag covers 3,600 sq ft
Supplies 1 lb of nitrogen per 1,000 sq ft, with 0 lb phosphate (P₂O₅) and 0.25 lb potash (K₂O) per 1,000 sq ft.
- Spreader settings differ by product and spreader: use the setting on the bag for this rate, and sweep granules off paths and drives.
How to use the seed and fertiliser calculator
- Measure the lawn as shapes and subtract beds, patios and the house.
- Seed: choose a new lawn or overseeding, then the grass. The rate fills in at the middle of the extension range, which is shown under it. If your seed bag gives a rate, type that instead, or pick Rate from my seed bag for a mix.
- Fertiliser: type the three numbers on the bag (N-P-K, such as 24-0-6) and the nitrogen you want to apply. The calculator divides the nitrogen by the N percentage: 1 lb of N per 1,000 sq ft from a 24% product is 1 ÷ 0.24 = 4.17 lb of product, the same sum LSU AgCenter and Illinois Extension show.
Where the rates come from
Seeding rates are from Penn State (cool-season grasses), the University of Georgia (warm-season grasses), Nebraska (overseeding tall fescue and bluegrass) and Colorado State (buffalograss). Where no overseeding rate is published, the calculator follows NC State's advice to sow 25–50% less into existing grass. Rates are in lb per 1,000 sq ft; multiply by 4.88 for g/m². For patching UK lawns the RHS suggests about 15–25 g/m².
For nitrogen, Illinois Extension advises no more than 1 lb of quick-release N per 1,000 sq ft at a time, and Minnesota Extension keeps each application to 1 lb or less, with 0.5 to 4 lb a year depending on how the lawn is kept.
Worked example
A 50 × 30 ft lawn is 1,500 sq ft. Tall fescue on bare soil at 6–8 lb per 1,000 sq ft needs 9–12 lb of seed; at 7 lb it is 10.5 lb. A 24-0-6 fertiliser at 1 lb N per 1,000 sq ft is 4.17 lb of product per 1,000 sq ft, or 6.25 lb for the lawn.
Sources
- Penn State Extension, Lawn establishment: seeding rates for tall fescue (6–8), Kentucky bluegrass (2–3), perennial ryegrass (4–5) and fine fescues (4–5 lb per 1,000 sq ft), and 4–6 lb of perennial ryegrass for overseeding.
- University of Georgia Extension, B1533-2 Lawns in Georgia: establishment, Table 3: bermudagrass (1–2 hulled, 3–6 unhulled), zoysiagrass (1–3), centipedegrass (¼–1) and bahiagrass (3–8 lb per 1,000 sq ft).
- University of Nebraska–Lincoln Turfgrass Science, Overseeding in the fall: tall fescue 3–4 lb per 1,000 sq ft when overseeding, Kentucky bluegrass about 2 lb.
- Colorado State University Extension, Buffalograss lawns: 3 to 5 lb of seed per 1,000 sq ft.
- NC State Extension, Carolina lawns: a 25 to 50 percent lower seeding rate when seeding into existing grass.
- Royal Horticultural Society, Repairing lawns: about 15–25 g of seed per m².
- University of Illinois Extension, Fertilizing your lawn, and LSU AgCenter, Calculating fertilizer application rates: dividing the nitrogen rate by the N fraction; no more than 1 lb of quick-release N per application.
- University of Minnesota Extension, Fertilizing lawns: each application no more than 1 lb N per 1,000 sq ft; 0.5 to 4 lb N a year.
- Minnesota Department of Agriculture, Phosphorus lawn fertilizer law: phosphorus-free lawn fertilizer unless a soil or tissue test shows a need or a new lawn is being established.
Seed and fertiliser questions
How much grass seed do I need per 1,000 sq ft?
It depends on the grass. For a new lawn Penn State gives 6–8 lb of tall fescue, 2–3 lb of Kentucky bluegrass and 4–5 lb of perennial ryegrass or fine fescues; the University of Georgia gives 1–2 lb of hulled bermudagrass and ¼–1 lb of centipedegrass. Follow the rate on your seed bag when it gives one.
How do I convert lb per 1,000 sq ft to g/m²?
Multiply by 4.88. One pound per 1,000 sq ft is 453.6 g spread over 92.9 m², or 4.88 g/m². So 7 lb per 1,000 sq ft is about 34 g/m², and 25 g/m² is about 5.1 lb per 1,000 sq ft.
How much 24-0-6 gives 1 lb of nitrogen per 1,000 sq ft?
Divide the nitrogen by the first number as a decimal: 1 ÷ 0.24 = 4.17 lb of product per 1,000 sq ft, or 20.8 lb for a 5,000 sq ft lawn. In metric, 4.9 g of N per m² ÷ 0.24 = 20.4 g of product per m².
How much seed do I need to overseed a lawn?
Less than for bare soil. Nebraska suggests 3–4 lb of tall fescue per 1,000 sq ft and about 2 lb of Kentucky bluegrass, and NC State 25–50% below the new-lawn rate; Penn State's overseeding rate for perennial ryegrass is 4–6 lb. For patching UK lawns the RHS suggests about 15–25 g/m².
Can I use a lawn fertiliser that contains phosphorus?
Check your local rules first. Minnesota, for example, requires phosphorus-free lawn fertilizer unless a soil or tissue test shows a need or a new lawn is being seeded or sodded. Other states and countries may have their own limits, so the calculator flags any phosphate in the product.