How much grass seed to buy
Seed labels and university extension services give seeding rates in pounds per 1,000 square feet. The rate depends mostly on seed size: Kentucky bluegrass has roughly 1 to 2 million seeds per pound, while tall fescue has only about 200,000, so fescue needs about three times the weight to put the same number of seeds on the ground. The calculator multiplies your lawn area by the rate for your grass type, divides by 1,000, and rounds up to whole bags.
Seeding rates used
| Grass | Typical range, new lawn | Calculator: new | Overseed |
|---|---|---|---|
| Tall fescue | 6–8 lb | 7 | 3.5 |
| Kentucky bluegrass | 2–3 lb | 2.5 | 1.25 |
| Perennial ryegrass | 5–9 lb | 6 | 3 |
| Fine fescue | 4–5 lb | 4.5 | 2.25 |
| Sun & shade mix | 4–6 lb | 5 | 2.5 |
| Bermuda (hulled) | 1–2 lb | 1.5 | 0.75 |
| Zoysia | 1–2 lb | 1.5 | 0.75 |
| Centipede | 0.25–0.5 lb | 0.5 | 0.25 |
Ranges follow extension recommendations such as Penn State's, and overseeding uses about half the new-lawn rate. Seed blends vary, so if your bag lists its own rate, choose "Custom rate" and enter it.
The formula
seed (lb) = lawn area × rate ÷ 1,000
bags = seed ÷ bag size, rounded up
cost = bags × price per bag
Example: a new 5,000 sq ft tall fescue lawn
| Step | Result |
|---|---|
| Seeding rate (tall fescue, new lawn) | 7 lb per 1,000 sq ft |
| Seed needed (5,000 × 7 ÷ 1,000) | 35 lb |
| Bags (35 ÷ 20 = 1.75) | 2 × 20 lb |
| Seed cost (2 × $55) | $110.00 |
Overseeding the same lawn needs 17.5 lb, so a single 20 lb bag covers it. Adding starter fertilizer at one 5,000 sq ft bag for $30 brings the new-lawn total to $140.
Tips for a thick lawn
- Seed-to-soil contact matters most. Loosen bare soil with a rake, or core-aerate or slit-seed an existing lawn before overseeding. Seed sitting on thatch rarely survives.
- Split the seed in half. Spread half walking one direction and half at right angles for even coverage.
- Keep it damp, not soaked. Water lightly once or twice a day until seedlings are about 2 in tall, then water deeper and less often. Tall fescue and ryegrass sprout in 7–14 days; bluegrass can take 3–4 weeks.
- Buy quality seed. Check the label for weed seed (ideally under 0.5%) and "other crop" content, and pick named turf-type varieties over cheap "contractor" mixes.
- Wait to mow and treat. Mow for the first time when grass reaches about one third above its target height, and skip most pre-emergent weed killers, which also stop grass seed from germinating.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
It depends on seed size. For a new lawn, Kentucky bluegrass needs about 2 to 3 pounds per 1,000 square feet, fine fescue 4 to 5, tall fescue 6 to 8, perennial ryegrass 5 to 9 and hulled bermudagrass 1 to 2. Overseeding an existing lawn uses about half those rates.
How much seed do I need for overseeding?
Overseeding a thin but living lawn usually takes about half the new-lawn rate, for example 3 to 4 pounds of tall fescue or 1 to 1.5 pounds of Kentucky bluegrass per 1,000 square feet. If more than half the lawn is bare, use the new-lawn rate instead.
Is it bad to put down too much grass seed?
Yes. Seeding far above the recommended rate makes seedlings compete for light, water and nutrients, which leads to thin, weak grass and more disease. Stick close to the label rate and focus on good seed-to-soil contact and steady moisture instead.
When is the best time to plant grass seed?
Plant cool-season grasses such as tall fescue, bluegrass and ryegrass in late summer to early fall, when soil is warm and air is cooling, with spring as a second choice. Plant warm-season grasses such as bermuda, zoysia and centipede in late spring to early summer once soil is consistently above about 65 degrees F.
How do I measure my lawn's square footage?
Break the lawn into rectangles, multiply length by width for each, and add them up, subtracting the house, driveway and beds. For a circle, multiply the radius squared by 3.14. Many online map tools can also measure an area from satellite imagery.
Do I need starter fertilizer when seeding?
It helps on new lawns and poor soil. Starter fertilizers are higher in phosphorus, which supports root growth in seedlings. Check local rules first, since some states and towns restrict phosphorus fertilizer unless a soil test shows a need or you are establishing new turf.
Rates and figures last checked September 2026.
This calculator gives estimates for planning. Check current rates and product labels before you buy, list or file.