How much grass seed do I need?
Seed is sown at a rate in pounds per 1,000 sq ft. The rate depends on the grass, because seed size varies a lot: a pound of Kentucky bluegrass holds far more seeds than a pound of ryegrass. Overseeding a thin lawn takes about half the rate of a new lawn.
Pounds of seed = area (sq ft) ÷ 1,000 × seeding rate (lb per 1,000 sq ft)
A new 50 × 40 ft lawn is 2,000 sq ft. Tall fescue is typically sown at 6–8 lb per 1,000 sq ft, so at 7 lb you need 2,000 ÷ 1,000 × 7 = 14 lb. That's two 7 lb bags.
Grass seed rates by type
| Grass | New lawn (lb per 1,000 sq ft) | Overseeding (lb per 1,000 sq ft) |
|---|---|---|
| Tall fescue | 6–8 | 3–4 |
| Kentucky bluegrass | 2–3 | 1–2 |
| Perennial ryegrass | 7–9 | 3–5 |
| Fine fescue | 4–5 | 2–3 |
| Bermudagrass, hulled | 1–2 | 0.5–1 |
| Zoysiagrass | 1–2 | 0.5–1 |
| Centipedegrass | 0.25–0.5 | 0.25 |
These are typical ranges from university extension guides. The calculator uses the middle of each range. Your seed bag lists its own rate, and that's the one to follow. For a blend, choose "Seed mix" and enter the label rate.
Grass seed calculator for overseeding
Overseeding fills in a thin lawn without starting over. Mow short, rake out thatch or run a slit seeder, then sow at about half the new-lawn rate. A 5,000 sq ft tall fescue lawn at 3.5 lb per 1,000 sq ft takes 17.5 lb, which is three 7 lb bags or one 20 lb bag.
Grass seed by square feet and per acre
If you know your lawn's square footage, choose "I know sq ft" and type it in. For large areas, multiply the rate by 43.56 to get pounds per acre. Tall fescue at 7 lb per 1,000 sq ft works out to about 305 lb per acre.
Cool-season and warm-season grass
Tall fescue, Kentucky bluegrass, ryegrass and fine fescue are cool-season grasses. They're typically seeded in late summer or early fall, with spring as the second choice. Bermuda, zoysia and centipede are warm-season grasses, seeded in late spring or early summer once the soil is warm. Your local extension office can tell you which grasses suit your area.
Getting seed to come up
Seed needs contact with soil. On bare ground, loosen the top inch or two, spread half the seed in one direction and half across it, rake it in lightly and roll. Keep the surface moist with light, frequent watering until the seedlings are established. Many lawns also get a starter fertilizer at seeding; see the fertilizer calculator.
Pricing a seeding job
Landscapers usually price seeding per 1,000 sq ft or per job, built from seed at cost plus markup and labor for prep, seeding, raking and rolling. Soil prep on a new lawn takes far longer than overseeding, and a slit seeder rental is a pass-through cost. Set your hours in contractor mode and add topsoil or straw lines to a landscaping estimate.
Questions
How much grass seed do I need for 1,000 sq ft?
It depends on the grass. Tall fescue typically takes 6–8 lb for a new lawn and 3–4 lb for overseeding. Kentucky bluegrass takes 2–3 lb for a new lawn.
How much grass seed do I need per acre?
Multiply the rate per 1,000 sq ft by 43.56. Tall fescue at 7 lb per 1,000 sq ft is about 305 lb per acre.
How much seed do I need to overseed a lawn?
About half the new-lawn rate. For tall fescue that's typically 3–4 lb per 1,000 sq ft.
Can I put down too much grass seed?
Yes. Sowing far above the label rate makes seedlings compete for light, water and nutrients, and the stand can thin out. Follow the rate on the bag.