Grass Seed Calculator
Enter the lawn size and grass type, and whether you are seeding bare ground or overseeding. You get the pounds of seed from extension-service rates, the bags to buy, and the cost.
Seed needed
19.2 lb
2,400 sq ft × 8 lb per 1,000
Buy
3 × 7 lb or one 20 lb
1 × 20 lb bags
Cost
$67
at $3.5/lb
Note
Cool-season
Large seed, bunch-type; the heaviest rate.
Seeding rates by grass type
Pounds per 1,000 sq ft, from university extension recommendations. Mixes: use the rate of the dominant grass by weight.
| Grass | Season | New lawn | Overseed | Note |
|---|---|---|---|---|
| Kentucky bluegrass | Cool | 3 lb | 1.5 lb | Tiny seed; slow to establish (2-4 weeks to germinate). |
| Tall fescue | Cool | 8 lb | 4 lb | Large seed, bunch-type; the heaviest rate. |
| Perennial ryegrass | Cool | 8 lb | 4 lb | Fast germination (5-7 days); common in mixes. |
| Fine fescue | Cool | 5 lb | 2.5 lb | Shade-tolerant; creeping red, chewings, hard. |
| Bermuda (hulled) | Warm | 1.5 lb | 0.75 lb | Very small seed; spreads by runners. |
| Zoysia | Warm | 2 lb | 1 lb | Slow from seed; often sodded or plugged. |
| Centipede | Warm | 0.5 lb | 0.25 lb | Low-input Southeast lawn; very light rate. |
| Bahia | Warm | 8 lb | 4 lb | Coarse Gulf Coast grass; heavy rate. |
| Buffalograss | Warm | 3 lb | 1.5 lb | Drought-tolerant plains native; burs are heavy. |
Pounds of seed by lawn size (new lawn)
| Area | Kentucky | Tall | Perennial | Fine | Bermuda | Zoysia |
|---|---|---|---|---|---|---|
| 1,000 sq ft | 3.0 | 8.0 | 8.0 | 5.0 | 1.5 | 2.0 |
| 2,500 sq ft | 7.5 | 20.0 | 20.0 | 12.5 | 3.8 | 5.0 |
| 5,000 sq ft | 15.0 | 40.0 | 40.0 | 25.0 | 7.5 | 10.0 |
| 7,500 sq ft | 22.5 | 60.0 | 60.0 | 37.5 | 11.3 | 15.0 |
| 10,000 sq ft | 30.0 | 80.0 | 80.0 | 50.0 | 15.0 | 20.0 |
| 21,780 sq ft (½ acre) | 65.3 | 174.2 | 174.2 | 108.9 | 32.7 | 43.6 |
| 43,560 sq ft (1 acre) | 130.7 | 348.5 | 348.5 | 217.8 | 65.3 | 87.1 |
Getting the seed to grow
- Seed-to-soil contact. Rake or core-aerate before sowing; seed sitting on thatch or bare hardpan does not germinate. Lightly rake or roll after.
- Water little and often. Keep the top half-inch damp -- 2-3 light waterings a day -- until germination, then taper to deeper, less frequent watering over four weeks.
- Starter fertilizer with phosphorus at seeding (where legal), then no more nitrogen for six weeks; the fertilizer page has the rates.
- Mow at 3 inches once it reaches 4, with a sharp blade. Skip pre-emergent herbicide for the season; it stops grass seed too.
Frequently Asked Questions
How much grass seed do I need per square foot?
It depends on the grass more than anything: tall fescue and ryegrass need about 8 lb per 1,000 sq ft for a new lawn, Kentucky bluegrass 3 lb, bermuda 1.5 lb, centipede half a pound. Overseeding an existing lawn takes half the new-lawn rate. For a 5,000 sq ft tall fescue lawn that is 40 lb new or 20 lb to overseed.
How much grass seed for an acre?
An acre is 43,560 sq ft: 348 lb of tall fescue, 131 lb of Kentucky bluegrass, 65 lb of hulled bermuda for a new stand. Pasture and utility mixes are sown lighter than lawns.
Is more seed better?
No. Seedlings sown too thickly compete for light and water, stay thin-stemmed and are more prone to damping-off; the lawn looks great at three weeks and thins at three months. Under-sowing leaves gaps weeds fill. Hit the rate, then spread half in each of two directions for even coverage.
When should I seed?
Cool-season grasses (bluegrass, fescue, ryegrass): late summer to early fall, when soil is warm and weeds are fading -- spring is second best. Warm-season grasses (bermuda, zoysia, centipede, bahia): late spring to early summer once soil is above 65°F. Seeding a cool-season lawn in late spring produces a lawn that dies in July.
Seed or sod?
Seed costs a tenth as much, offers every cultivar, and is the only option for some grasses, but takes a season to become a lawn and needs watering twice a day for the first two weeks. Sod is a lawn in a day at 10-20 times the price, and some warm-season grasses are only practical as sod. The sod calculator sizes that job.
These calculators use published seeding rates, extension-service fertilizer guidance, and standard pool-chemistry dosing figures, and are for planning. Read the product label; it governs the dose. Pool chemicals are hazardous when mixed or mishandled, and a pool store's water test beats any estimate here.