Our grass seed calculator uses one sourced figure for each grass. Use these tables to see the range behind it and to find the figure your own region's extension service recommends.
New lawns
A new lawn is sown on bare, prepared soil, so the seed has to fill every gap on its own. These are the rates each extension service prints for that job.
| Grass | Penn State | NC State | Purdue | Illinois | Florida |
|---|---|---|---|---|---|
| Kentucky bluegrass | 2–3 | 1–2 | 1.5–2.0 | 3 | – |
| Tall fescue | 6–8 | 6 | 6.0–9.0 | 5–10 (fescue or ryegrass) | – |
| Perennial ryegrass | 4–5 | – | – | 5–10 (fescue or ryegrass) | – |
| Fine fescues | 4–5 | – | – | – | – |
| Bluegrass and ryegrass mix | 2–3 | – | 3.0–4.0 | – | – |
| Bluegrass and fine fescue mix | 3–4 (with some ryegrass) | – | 4.0–5.0 | – | – |
| Bermudagrass (hulled seed) | – | 1–2 | – | – | 1–2 |
| Zoysiagrass | – | 1–2 | – | – | – |
| Centipedegrass | – | 0.25–0.5 | – | – | 0.25 (4 oz) |
Purdue's per-acre column for tall fescue works out to a narrower range than its per-thousand-square-feet column; the table shows the per-thousand figure as printed. Florida's centipedegrass figure comes from its centipedegrass guide, listed under Sources.
Overseeding an existing lawn
Overseeding thickens turf that is already growing. Fewer extension guides give separate figures for it, and the ones that do mostly suggest less seed than for a new lawn.
| Grass | Penn State | Illinois | NC State |
|---|---|---|---|
| Kentucky bluegrass | – | 1.5 | may be 25–50% below the new-lawn rate |
| Tall fescue | – | 3–5 (fescue or ryegrass) | may be 25–50% below the new-lawn rate |
| Perennial ryegrass | 4–6 (overseeding or renovation) | 3–5 (fescue or ryegrass) | may be 25–50% below the new-lawn rate |
NC State gives one general rule for seeding into existing grass rather than a figure for each species.
Why the figures differ
- Region. Each extension service writes for its own state's climate, soils and grass varieties.
- Seed size. Small-seeded grasses such as bluegrass and centipedegrass need far fewer pounds than large-seeded tall fescue to cover the same ground.
- Blends. A mix is seeded at a rate between those of its parts, weighted by how much of each grass it holds.
- Goal. A higher rate fills in faster; a lower rate costs less and leaves seedlings more room. Follow the rate on your seed label when it differs.
From a rate to pounds of seed
Multiply the rate by the lawn's area in thousands of square feet to get the pounds to buy, then round up to whole bags. The grass seed calculator does this for each grass and job.
If you are weighing seed against laid turf, size the same lawn with the sod calculator, and plan the feeding that follows with the fertilizer calculator.
Common questions
How much grass seed do I need per thousand square feet?
It depends on the grass. The tables run from a fraction of a pound for centipedegrass to several pounds for tall fescue, because seed size varies so much between grasses.
Should I use less seed when overseeding?
Usually. NC State suggests a lower rate when seeding into existing grass, and Illinois lists lower overseeding rates than new-lawn rates. Penn State's overseeding figure for perennial ryegrass sits close to its new-lawn range.
Which figure should I use?
Start with the extension service for your own region, then check the label on the seed you buy. Blends and coated seed often carry their own rate.
Using these figures
You are welcome to cite the tables on this page. Please link to this page as the source, and check the maker's current data sheet before you rely on a single figure.