Grass Seed Calculator: How Much Grass Seed Do I Need?

How to use the grass seed calculator

1. Choose the job. “New lawn” is for seeding prepared ground with no grass on it. “Overseed” is for thickening an existing lawn, which takes less seed per square foot.
2. Pick the grass. Cool-season grasses (tall fescue, Kentucky bluegrass, perennial ryegrass, fine fescue) suit the North and the transition zone. Warm-season grasses (bermuda, zoysia, centipede) suit the South. The last option is ryegrass sown over a dormant warm-season lawn for winter color.
3. Enter the area. Use length × width, or type the square footage if you have already added up an irregular lawn.
4. Add bare spots when overseeding. Enter the bare patches inside the lawn. The calculator seeds them at the new-lawn rate and the rest at the overseeding rate.
5. Set the bag size.

The main figure uses the high end of the rate range, which is what we suggest you buy. The low end is shown next to it. UMass Extension notes that seeding below the recommended rate leaves a thin stand that weeds move into, so cutting back on seed rarely saves money. The same guide suggests about 50% more seed where conditions are poor, such as compacted soil, a rough seedbed or a steep slope.

How much grass seed do I need? The formula

Seeding rates are always given per 1,000 sq ft. They vary widely by species because seed size varies widely. A pound of Kentucky bluegrass contains far more seeds than a pound of tall fescue. Wisconsin’s extension table shows this. At 1 to 1.5 lb, bluegrass puts 15 to 23 seeds on every square inch. Tall fescue needs 7 to 9 lb to reach 11 to 14 seeds per square inch. That is why the bluegrass rate looks so small next to tall fescue.

Overseeding takes less seed because the lawn is already partly covered. Illinois Extension suggests 3 to 5 lb per 1,000 sq ft for fescue and ryegrass and 1.5 lb for bluegrass when overseeding, and the full new-lawn rate in bare spots. Nebraska’s turfgrass program gives 3 to 4 lb for tall fescue and about 2 lb for bluegrass. Advice does differ, though. Wisconsin’s guide says to use twice its table rate when broadcasting into a thin lawn after core aeration, or about 20% more in a partial renovation, because some seed lands on thatch and never reaches soil. If you are broadcasting over heavy thatch, use the new-lawn mode instead.

Coated seed carries a clay or fertilizer coating that adds weight. Arkansas Extension notes that coated seed needs higher seeding rates. With coated seed, follow the rate on the bag instead of these figures.

Worked examples

New tall fescue lawn, 5,000 sq ft

5 × 7 = 35 lb to 5 × 9 = 45 lb. Buy 45 lb, two 25 lb bags.

Overseeding 5,000 sq ft of tall fescue

5 × 3 = 15 lb to 5 × 4 = 20 lb. One 25 lb bag covers it. If you broadcast without aerating or slit-seeding first, more seed lands on thatch, so plan on the high end or more.

Blend lawn, 4,000 sq ft overseeded with 300 sq ft of bare spots

The 3,700 sq ft of thin lawn needs 11.1 to 18.5 lb at the overseeding rate of 3 to 5 lb. The 300 sq ft of bare spots needs 1.5 to 2.1 lb at the new-lawn rate of 5 to 7 lb. Together that is 12.6 to 20.6 lb.

Bermudagrass, 6,000 sq ft

At 0.5 to 1 lb per 1,000 sq ft, you need 3 to 6 lb of hulled seed. Arkansas recommends seeding warm-season grasses in May and June.

Winter rye over a dormant bermuda lawn, 5,000 sq ft

6 to 10 lb per 1,000 sq ft comes to 30 to 50 lb, one 50 lb bag. It is sown in fall for green color through winter.

Grass seed rates by type (lb per 1,000 sq ft)

A dash means none of our sources gave a separate rate. Warm-season grasses spread by stolons or rhizomes and fill thin spots themselves, so bare areas in those lawns are seeded at the new-lawn rate. For fine fescue, use the new-lawn rate on bare spots and a lighter hand elsewhere.

When and how to seed

• Cool-season grasses: Wisconsin names late summer to early autumn, mid-August to mid-September, as the best time to seed. Early spring is the next best. Arkansas gives September to October for tall fescue.
• Warm-season grasses: Arkansas lists May to June for bermuda, zoysia and centipede. Clemson gives late spring to early summer for zoysia seed.
• Spread in two directions. Split the seed in half and spread one half north–south and the other east–west, as both Wisconsin and Arkansas advise.
• Get seed into the soil. Rake it lightly into the top ¼ in and roll or tamp it. Good seed-to-soil contact keeps the seed from drying out. Core aerating before overseeding makes holes for seed to land in, Illinois Extension notes.
• Keep it moist. Water at least once a day for two to three weeks, and lightly enough that seed does not float away. Bluegrass can take two to four weeks to germinate.

Seeding bare ground or a low spot? Spread a layer of good soil first. The topsoil calculator works out cubic yards and bags for any area and depth. The mulch calculator covers the beds around the new lawn.

Sources & assumptions

How this calculator gets its numbers. Full method: our methodology.

• Seed = area ÷ 1,000 × rate. The headline figure uses the high end of each rate range, and the low end is shown beside it. Bags are rounded up at the high rate.
• When overseeding, bare spots are seeded at the new-lawn rate (Illinois Extension). Where a source gives no overseeding rate (warm-season grasses, fine fescue), the new-lawn rate is used. Where it gives only an overseeding rate (winter ryegrass), that rate is used.
• Rates are for raw (uncoated) seed. Coated seed needs higher rates, so follow the bag.
• Rates differ between universities. Wisconsin advises up to twice its table rate when broadcasting into a thin lawn, so increase the rate if seed will land on thatch.

Sources

1. University of Wisconsin–Madison Extension, Lawn Establishment (A3434). Table 2 new-lawn rates (tall fescue and ryegrass 7–9, creeping red fescue 3.5–4.5 lb); mid-August to mid-September timing; two-direction spreading.
2. University of Nebraska–Lincoln Turfgrass Science, Overseeding in the Fall. Overseed Kentucky bluegrass at about 2 lb (1–3 new) and tall fescue at 3–4 lb (5–8 new) per 1,000 ft².
3. University of Illinois Extension, Lawn aeration and overseeding. Overseed fescue and ryegrass 3–5 lb, bluegrass 1.5 lb; new-lawn rate in bare spots.
4. University of Arkansas Cooperative Extension Service, Lawn Establishment (FSA2113). Table 3 rates and timing for blends and warm-season grasses; coated seed needs higher rates.
5. Clemson Cooperative Extension, Home & Garden Information Center, Zoysiagrass. Zenith zoysia seeded in late spring to early summer at 1–2 lb per 1,000 ft².
6. UMass Amherst Extension, Seeding Rate Considerations. Under-seeding gives an open stand that invites weeds; over-seeding gives many immature plants slow to toughen up; increase about 50% for poor conditions.

Last reviewed October 25, 2026. Product figures vary by brand; the label on what you buy wins.