How to calculate grass seed
Grass seed is sold by weight, and seeding rates are given in pounds per 1,000 square feet. Measure the area you will seed, divide by 1,000, and multiply by the rate for your grass. Then divide by the bag size and round up.
Seed (lb) = area (sq ft) ÷ 1,000 × seeding rate (lb per 1,000 sq ft)
Bags = seed (lb) ÷ bag size (lb), rounded up
The rate depends on the size of the seed. Kentucky bluegrass has very small seeds, so 2–3 lb covers 1,000 sq ft. Tall fescue seeds are much larger, so the same area takes 6–8 lb. That is why a "how much seed" answer without the grass type is not useful.
Worked example: a 50 × 40 ft new lawn of tall fescue
- Area: 50 × 40 = 2,000 sq ft.
- Thousands of square feet: 2,000 ÷ 1,000 = 2.
- Seed at 7 lb per 1,000 sq ft (the middle of the 6–8 lb range): 2 × 7 = 14 lb.
- Bags: 14 ÷ 7 = 2 bags of 7 lb (or 5 bags of 3 lb, or 1 bag of 20 lb).
Overseeding the same lawn at 3.5 lb per 1,000 sq ft takes 2 × 3.5 = 7 lb, which is one 7 lb bag.
Seeding rates by grass type
The ranges below are typical of those published by US university extension services for uncoated seed. The calculator uses the middle of each range. Your state extension office may recommend slightly different numbers for your region, and a seed label's own rate always takes priority.
| Grass | Type | New lawn (lb per 1,000 sq ft) | Overseeding (lb per 1,000 sq ft) | Typical germination |
|---|---|---|---|---|
| Tall fescue | Cool-season | 6–8 | 3–4 | About 7–14 days |
| Kentucky bluegrass | Cool-season | 2–3 | 1–2 | About 14–30 days |
| Perennial ryegrass | Cool-season | 5–8 | 3–5 | About 5–10 days |
| Fine fescue (creeping red, chewings, hard) | Cool-season | 3–5 | 1.5–2.5 | About 7–14 days |
| Bermudagrass, hulled | Warm-season | 1–2 | 0.5–1 | About 7–21 days in warm soil |
| Zoysiagrass | Warm-season | 1–2 | 0.5–1 | About 14–21 days |
| Centipedegrass | Warm-season | 0.25–0.5 | About half the new-lawn rate | About 14–28 days |
| Bahiagrass | Warm-season | 5–10 | 3–5 | About 3–4 weeks or longer |
More seed is not better. Seeding well above the range crowds the seedlings, so they compete for water and light, stay thin and weak, and are more prone to disease. Stay within the range and fix thin spots with a second, light seeding a few weeks later.
Coated seed, mixes and the seed label
- Coated seed covers less per pound. Some seed comes with a coating that helps hold moisture or carries fertilizer. The coating can be a large share of the weight, so a pound contains fewer seeds. Use the coverage printed on the bag and enter it as a custom rate.
- Mixes have their own rate. Sun-and-shade mixes usually combine Kentucky bluegrass, perennial ryegrass and fine fescue, and the label gives a rate for the blend. Use it with the custom option. Tall fescue blends that contain a little bluegrass are usually seeded at about the tall fescue rate.
- Read the analysis tag. It lists each grass by percent of weight, the germination rate and the weed seed content. Higher germination and lower weed and "other crop" content mean more lawn per pound.
When to plant grass seed in the US
Cool-season grasses (tall fescue, bluegrass, ryegrass, fine fescue) grow across the northern states and the transition zone. The best time to seed is late summer to early fall, roughly mid-August through September in much of the North. The soil is still warm, nights are cool and weeds are slowing down. Spring seeding is the backup plan; seedlings then have to survive summer heat, and most crabgrass preventers also stop grass seed from sprouting unless the product is labeled for use at seeding.
Warm-season grasses (bermudagrass, zoysia, centipede, bahiagrass) grow across the South. Seed them in late spring to early summer, once soil stays about 65°F or warmer, and give the seedlings at least two to three months of warm weather before the first fall frost.
Getting seed to grow
- Get seed-to-soil contact. Seed sitting on top of thatch or hard soil dries out. For a new lawn, loosen and rake the soil smooth first; our topsoil calculator helps if you need to build up the grade. For overseeding, mow short, rake out thatch, and core aerate or rent a slit seeder.
- Spread in two passes. Split the seed in half and apply each half in perpendicular directions with a broadcast or drop spreader. This avoids stripes and bare gaps.
- Cover lightly. Rake so seed is covered about 1/8 to 1/4 in., then roll it with an empty lawn roller. A thin layer of clean straw helps on slopes and in wind.
- Keep the surface moist. Water lightly once or twice a day, more in hot or windy weather, so the top of the soil never dries out until the grass is up. Then water less often but more deeply.
- Feed and mow on schedule. A starter fertilizer helps new lawns; see the fertilizer calculator and follow the product label and your state's fertilizer rules. Mow for the first time once the new grass is about a third taller than your mowing height.
If you would rather have an instant lawn, compare the cost with the sod calculator.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
It depends on the grass. For a new lawn, typical rates are about 6–8 lb for tall fescue, 2–3 lb for Kentucky bluegrass, 5–8 lb for perennial ryegrass and 1–2 lb for hulled bermudagrass per 1,000 sq ft. Overseeding an existing lawn takes roughly half as much.
How much grass seed do I need for an acre?
An acre is 43,560 sq ft, or 43.56 thousand square feet. A new tall fescue lawn at 7 lb per 1,000 sq ft takes about 305 lb per acre; Kentucky bluegrass at 2.5 lb takes about 109 lb. Pasture and roadside seeding rates are different from lawn rates.
Can you put down too much grass seed?
Yes. Seeding well above the recommended rate packs seedlings so tightly that they compete for water, light and nutrients. The result is a thin, weak stand that is more prone to disease. It also wastes money.
When is the best time to plant grass seed?
For cool-season grasses like tall fescue and Kentucky bluegrass, late summer to early fall is best, with spring as a second choice. For warm-season grasses like bermudagrass and zoysia, plant in late spring to early summer once soil stays about 65°F or warmer.
How long does grass seed take to grow?
Perennial ryegrass often sprouts in about 5–10 days and tall fescue in about 7–14 days. Kentucky bluegrass can take 2–4 weeks, and bahiagrass and centipedegrass are slow as well. Keep the soil surface moist the whole time; seed that dries out after it starts to sprout usually dies.
Should I cover grass seed with topsoil?
Not with a thick layer. Rake the seed in so it is covered about 1/8 to 1/4 in. deep and roll it for good contact. Burying it deeper slows or prevents germination. A thin layer of clean straw is fine for holding moisture and preventing washouts.
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