Early fall is the best time to overseed cool-season lawns: warm soil speeds germination and cooler air and fall rain help the seedlings establish before winter.
How the grass seed calculator works
GrassSeedCalc multiplies your lawn area in thousands of square feet by the seeding rate for the grass you choose. The rates are midpoints of the ranges published by US university extension services, in pounds of pure, uncoated seed per 1,000 square feet: the full rate for a new lawn on bare soil, and about half for overseeding an existing lawn. Coated seed can be up to half coating by weight, so the coated option doubles the rate. Bags are rounded up to whole bags, and the per-acre figure is the rate × 43.56, since an acre is 43,560 square feet. Areas in acres or square metres are converted to square feet first.
Seeding rates by grass type
| Grass | New lawn (lb/1,000 sq ft) | Overseed (lb/1,000 sq ft) | New lawn (lb/acre) | Type |
|---|---|---|---|---|
| Tall fescue | 8 | 4 | 348 | cool-season |
| Kentucky bluegrass | 2.5 | 1.5 | 109 | cool-season |
| Perennial ryegrass | 7 | 4 | 305 | cool-season |
| Fine fescue | 4.5 | 2.5 | 196 | cool-season |
| Sun & shade mix | 5 | 2.5 | 218 | cool-season |
| Bermudagrass (hulled) | 1.5 | 1 | 65 | warm-season |
| Zoysiagrass | 1.5 | 1 | 65 | warm-season |
| Centipedegrass | 0.5 | 0.25 | 22 | warm-season |
| Bahiagrass | 8 | 5 | 348 | warm-season |
| Buffalograss | 2.5 | 1.5 | 109 | warm-season |
Follow the rate on your seed bag when it differs: blends, mixes and seed quality vary. Germination needs good seed-to-soil contact and steady moisture. Results are estimates.
Frequently asked questions
How much seed do I need to overseed?
About 4 lb per 1,000 sq ft for tall fescue or perennial ryegrass, 1.5 lb for Kentucky bluegrass and 2.5 lb for fine fescue.
Should I aerate before overseeding?
Core aerating or slit seeding first gives the seed contact with soil, which greatly improves germination.
Can I overseed warm-season lawns?
Many southern lawns are overseeded with ryegrass for winter color; use about 5–10 lb per 1,000 sq ft for that purpose.
Is GrassSeedCalc free?
Yes, with no sign-up or ads.
Are my numbers saved?
Yes, in this browser only.