How to calculate grass seed
Seeding rates are given per 1,000 square feet, so the formula is:
Pounds of seed = (Lawn area ÷ 1,000) × rate
A 50 ft × 40 ft lawn is 2,000 square feet. At a new-lawn rate of 5 lb per 1,000 sq ft, that's (2,000 ÷ 1,000) × 5 = 10 pounds of seed.
New lawn vs. overseeding
- New lawn: 4–6 lb per 1,000 sq ft over prepared, bare soil.
- Overseeding: 2–3 lb per 1,000 sq ft to thicken an existing lawn.
Pick the purpose above to set the rate automatically, or choose Custom to enter your bag's recommended rate.
Timing matters
Cool-season grasses establish best in early fall; warm-season grasses prefer late spring. Seeding in the right window — and keeping the seedbed consistently moist — makes a bigger difference than slightly more or less seed.
Frequently asked questions
How much grass seed do I need?
Multiply your lawn area in square feet by the seeding rate, then divide by 1,000, since rates are given per 1,000 square feet. A 2,000 sq ft lawn at a new-lawn rate of 5 lb per 1,000 sq ft needs 10 pounds of seed.
What is the right seeding rate?
It depends on the grass and the job. New lawns typically need 4–6 lb per 1,000 sq ft, while overseeding an existing lawn uses about half that — 2–3 lb per 1,000 sq ft. Always check the rate on your specific seed bag, as it varies by species and blend.
When should I plant grass seed?
For cool-season grasses (fescue, ryegrass, bluegrass), early fall is best, with spring second. For warm-season grasses (Bermuda, zoysia), late spring into early summer once the soil has warmed. Seeding in the right window dramatically improves germination.
Should I overseed or start a new lawn?
Overseed if your lawn is thin but mostly healthy — it fills in gaps at the lower rate. Start fresh (full rate, often with soil prep) if the area is bare, heavily weeded, or being newly established. Choose the matching rate above.
Disclaimer: Always follow the rate printed on your seed bag, which varies by species and blend. This is a planning estimate.