---
title: "Grass Seed & Lawn Fertiliser Calculator | Moss Landings"
description: "Grass seed by grass type for a new lawn or overseeding, in lb per 1,000 sq ft or g/m², and fertiliser from the N-P-K label to hit a nitrogen rate."
url: https://mosslandings.homes/grass-seed-fertilizer-calculator/
---

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.

## How to use the seed and fertiliser calculator

1. **Measure the lawn** as shapes and subtract beds, patios and the house.
2. **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.
3. **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](https://extension.psu.edu/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](https://fieldreport.caes.uga.edu/publications/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](https://turf.unl.edu/news/overseeding-fall/): tall fescue 3–4 lb per 1,000 sq ft when overseeding, Kentucky bluegrass about 2 lb.
- Colorado State University Extension, [Buffalograss lawns](https://extension.colostate.edu/resource/buffalograss/): 3 to 5 lb of seed per 1,000 sq ft.
- NC State Extension, [Carolina lawns](https://content.ces.ncsu.edu/carolina-lawns): a 25 to 50 percent lower seeding rate when seeding into existing grass.
- Royal Horticultural Society, [Repairing lawns](https://www.rhs.org.uk/lawns/repairing): about 15–25 g of seed per m².
- University of Illinois Extension, [Fertilizing your lawn](https://extension.illinois.edu/lawns/fertilizing-your-lawn), and LSU AgCenter, [Calculating fertilizer application rates](https://www.lsuagcenter.com/topics/lawn_garden/home_gardening/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](https://extension.umn.edu/lawn-care/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](https://www.mda.state.mn.us/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.