How much grass seed do I need for a new lawn?

Cool-season new-lawn rates are roughly 2 lb per 1,000 sq ft for Kentucky bluegrass, 4 lb for fine fescue, and 8 lb for tall fescue and perennial ryegrass. Warm-season new-lawn rates are 1.5 lb for bermudagrass, 2 lb for zoysia, 0.5 lb for centipede, and 7 lb for bahiagrass. A 5,000 sq ft tall fescue lawn needs 40 lb of seed; a 5,000 sq ft bermudagrass lawn needs 7.5 lb.

How much seed for overseeding?

Overseeding uses roughly half the new-lawn rate because you are adding seed to an existing stand of grass. For tall fescue, that is 4 lb per 1,000 sq ft; for Kentucky bluegrass, 1 lb; for perennial ryegrass, 4 lb. Overseed in early fall for cool-season grasses and in late spring for warm-season grasses. Aerate first so seed can reach soil.

When should I plant grass seed?

Cool-season grasses germinate best in early fall (August 15 to September 15 in most of the US) when soil is warm and air is cool. Spring planting works but has more weed competition. Warm-season grasses go in late spring to early summer after soil reaches 65°F consistently. Never seed in summer heat or during a freeze.

Kentucky bluegrass vs tall fescue — how much seed?

Kentucky bluegrass has very small seeds (about 2 million seeds per pound), so a 2 lb per 1,000 sq ft rate still delivers 4 million seeds per 1,000 sq ft. Tall fescue has much larger seeds (about 227,000 per pound), so even at 8 lb per 1,000 sq ft the seed count is lower — just under 2 million. Both rates produce a thick lawn; they just reflect seed size.

Can I use too much grass seed?

Yes. Over-seeding makes seedlings compete for light, water, and nutrients, producing weak grass that fails to thicken. Stick to the recommended rate for your species. If seed has been sitting for more than 2 years, germination drops 10 to 20 percent per year, so increase the rate 25 percent for old seed — but never double-up for a perceived fast fill.

Grass Seed Calculator - How Much Seed Do I Need?

How many pounds of grass seed do you need for a new lawn or overseeding? Enter your lawn area and grass type to see the correct species-specific rate.

How Much Grass Seed Do You Need?

Grass seeding rates are always expressed as pounds of seed per 1,000 square feet, and they vary dramatically by species because seeds vary in size, germination rate, and seedling vigor. Tiny Kentucky bluegrass seeds need less weight per area because there are 2 million seeds in a pound; coarse tall fescue has only 227,000 seeds per pound and needs four times the weight for the same seedling count. The calculator uses extension-service recommended rates and halves them for overseeding. Default example: a 5,000 sq ft tall fescue lawn at the new-lawn rate of 8 lb per 1,000 sq ft needs 40 lb of seed.

Cool Season vs Warm Season Grasses

Cool-season grasses dominate the northern US — roughly north of I-40. They include Kentucky bluegrass, tall fescue, fine fescue, and perennial ryegrass. They grow vigorously in spring and fall, slow or dormant in summer heat. Warm-season grasses rule the south — Gulf Coast up through the transition zone. They include bermudagrass, zoysia, St. Augustine, centipede, and bahiagrass. They grow in summer and go dormant below 55°F. Mixing the two types in one lawn produces patchy results; pick one appropriate to your climate.

How to Seed a New Lawn

Kill existing vegetation if any, either by sheet-mulching with cardboard for a month or using a grass-and-weed killer. Till or aerate the soil to a depth of 4 inches, rake smooth, and remove debris. Spread a starter fertilizer (high phosphorus for rooting). Broadcast half your seed walking north-south, then the other half walking east-west for even coverage. Lightly rake to cover most seed with 1/8 to 1/4 inch of soil — too deep and the seeds won't germinate. Water lightly every day until germination (5 to 14 days), then taper.

Overseeding an Existing Lawn

Overseed a cool-season lawn in early fall, a warm-season lawn in late spring. Mow the existing grass short, rake out dead material, and core-aerate to open soil for seed. Broadcast seed at half the new-lawn rate, top with a thin layer of compost or soil to ensure good seed-to-soil contact, and water daily until germination. Avoid pre-emergent herbicides in the 8 weeks before and after seeding — they prevent seed from sprouting.

Frequently Asked Questions

Best time to plant grass seed?

Early fall for cool-season; late spring for warm-season.

How long does grass seed take to germinate?

Ryegrass 5–7 days, tall fescue 7–14 days, Kentucky bluegrass 14–30 days.

Do I need a lawn starter fertilizer?

Yes — starter fertilizers are high in phosphorus to support root development.

How often should I water new grass seed?

Lightly twice a day until germination, then daily, then taper over the first 4 weeks.

Can you seed over old grass?

Yes with proper prep: mow short, rake, aerate, then seed. Expect a 50 to 70 percent catch.

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