Grass Seed Calculator
Different grasses need very different seeding rates — pick your type and lawn size, and buy exactly what you need.
How to use the Grass Seed Calculator
- Measure your lawn area (or the patch you are seeding).
- Pick your grass type — seeding rates vary 5× between species.
- Choose new lawn or overseeding (overseeding uses about half the rate).
- Buy slightly more than calculated — seed does not keep well year to year.
Formula & methodology
Seed (lb) = Area (ft²) ÷ 1,000 × rate per 1,000 ft² × project factor. Rates (new lawn): Kentucky bluegrass ~2.5 lb, perennial ryegrass ~5.5 lb, tall fescue ~8 lb, fine fescue ~4.5 lb, Bermuda ~1.5 lb. Overseeding ≈ 50% of new-lawn rate.
Example
Overseeding a 50 ft × 40 ft lawn (2,000 ft²) with tall fescue: 2 × 8 × 0.5 = 8 lb of seed — buy a 10 lb bag.
Related calculators
FAQ
How much grass seed for a new lawn?
It depends on species: roughly 1.5 lb (Bermuda) to 8 lb (tall fescue) per 1,000 ft². The calculator applies the right rate automatically.
How much seed for overseeding?
About half the new-lawn rate. Thick-cut thin lawns in fall — seed meets soil best when existing grass is short.
Can I put down too much grass seed?
Yes — overseeded grass competes with itself, grows thin and weak, and invites fungus. Follow the rate for your species.
When is the best time to plant grass seed?
Cool-season grasses (fescue, bluegrass, ryegrass): late summer–early fall. Warm-season (Bermuda, zoysia): late spring. Soil temperature drives germination more than air temperature.