How the seed amount is calculated
Seed needed scales directly with lawn area and the seeding rate recommended for your grass type — coarser, larger-seeded grasses need a heavier rate per square meter.
- area — width × length, in square meters
- rate — seeding rate for the selected grass type (g/m²)
More detail
Seeding rates by grass type
Reference rates (new lawn establishment): Kentucky bluegrass ≈12 g/m², tall fescue ≈35 g/m², perennial ryegrass ≈40 g/m². Fine-seeded bluegrass needs far less by weight than the larger-seeded fescues and ryegrass to reach the same seed density per area.
Practical tip. For overseeding an existing lawn, half the new-lawn rate is usually enough since you're filling gaps, not starting from bare soil. Split the total in two passes — lengthwise then crosswise — for more even coverage.
Frequently asked questions
How much seed do I need for a 10m × 5m lawn of tall fescue?
10m × 5m = 50 m² of area, and tall fescue's reference rate is about 35 g/m², so 50 × 35 = 1,750 g (1.75 kg) of seed. Enter your own width, length, and grass type above for the exact amount.
Why does Kentucky bluegrass need so much less seed than tall fescue?
Kentucky bluegrass seeds are much smaller and lighter than tall fescue or perennial ryegrass seeds, so far fewer grams are needed to reach the same number of seeds per square meter — its reference rate (≈12 g/m²) is roughly a third of tall fescue's (≈35 g/m²).
Is this the same rate for overseeding an existing lawn?
No — these are new-lawn establishment rates. Overseeding a thin but existing lawn typically needs about half this amount, since you're filling gaps rather than covering bare soil.
Where do these seeding rates come from?
They're reference values from Penn State Extension's turfgrass establishment guidance, converted from lb/1,000 ft² to g/m². Always check your specific seed product's label, since blends and cultivars vary.