Grass Seed Calculator
Pounds of seed by lawn size, grass type, and seeding rate.
You need
8.0 lb
Rates vary by blend; check the bag and use its number if it differs.
- Lawn area
- 1,000 sq ft
- A 20 lb bag covers
- 2,500 sq ft
Estimates only. Verify quantities before ordering.
How this is calculated
Seed = lawn area / 1,000 x rate for the selected grass and job. Rates: tall fescue 8 lb new or 4 lb overseed, Kentucky bluegrass 3 lb new, perennial ryegrass 9 lb new, sun and shade mix 5 lb new, per 1,000 sq ft.
Enter the lawn dimensions and pick the grass type and job, and this calculator converts the standard seeding rate (pounds per 1,000 square feet) into the total seed to buy. New lawns use roughly double the overseeding rate because bare soil needs full coverage, while overseeding just thickens what is already growing.
More seed is not better. Seeding far above the recommended rate crowds seedlings into weak, spindly grass that is more prone to disease, and it wastes money. If your number lands between bag sizes, round up modestly and spread the extra over thin areas rather than doubling the rate everywhere.
Seed for common lawn sizes
Rows show tall fescue at the new-lawn rate of 8 lb per 1,000 sq ft; overseeding uses about half.
| Lawn size | Seed | Area |
|---|---|---|
| 20 x 25 ft (500 sq ft) | 4.0 lb | 500 sq ft |
| 25 x 40 ft (1,000 sq ft) | 8.0 lb | 1,000 sq ft |
| 50 x 50 ft (2,500 sq ft) | 20.0 lb | 2,500 sq ft |
| 50 x 100 ft (5,000 sq ft) | 40.0 lb | 5,000 sq ft |
| 100 x 100 ft (10,000 sq ft) | 80.0 lb | 10,000 sq ft |
Common questions
How much grass seed per square foot?
Rates are quoted per 1,000 square feet and differ by species because seed sizes differ enormously. Tall fescue runs about 8 lb per 1,000 for a new lawn, perennial ryegrass 8 to 10, but Kentucky bluegrass only 2 to 3 because its seed is tiny. Overseeding uses about half the new-lawn rate.
When is the best time to plant grass seed?
For the cool-season grasses this calculator covers (fescue, bluegrass, ryegrass), early fall is best: warm soil, cooler air, and a full season before summer stress. Spring is second best. Warm-season grasses like bermuda are seeded in late spring instead.
Why is bluegrass seeded so much lighter than fescue?
Kentucky bluegrass seed is far smaller, so a pound contains around two million seeds versus roughly a quarter million for tall fescue. Bluegrass also spreads by rhizomes and fills in on its own, while fescue is a bunch grass that only thickens where seed actually lands.
Should I put topsoil or straw over new seed?
Seed wants firm contact with soil, not burial: rake it lightly so it sits within about 1/4 inch of the surface. A thin scattering of clean straw or a seeding mulch helps hold moisture on slopes and hot sites, but you should still see about half the soil through it.