Grass Seed Calculator
Calculate how many pounds of grass seed you need for a new lawn or overseeding. Uses standard seeding rates for fescue, bluegrass, ryegrass, Bermuda and zoysia.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Grass seed needed
- 8 lb
- 8 lb per 1,000 sq ft for a new lawn
- Area to seed
- 1,000 sq ft
- Bags to buy
- 3 bags of 3 lb
- Or 2 bags of 7 lb, or 1 bag of 20 lb
- Starter fertilizer
- 1 bag
- A typical starter fertilizer bag covers 5,000 sq ft; apply at seeding
Grass Seed formula
Lawn area = Length (ft) x Width (ft) + Extra area
Seed (lb) = Lawn area / 1,000 x seeding rate
New lawn rates: bluegrass 3, tall fescue 8, ryegrass 9, fine fescue 5, Bermuda 2, zoysia 2 lb per 1,000 sq ft
Overseeding rates are half the new lawn rateWorked example
Overseeding a thin 60 x 40 ft Kentucky bluegrass lawn: 60 x 40 = 2,400 sq ft. 2,400 / 1,000 = 2.4, and 2.4 x 1.5 lb = 3.6 lb of seed. Two 3 lb bags or one 7 lb bag covers it.
A new perennial ryegrass lawn 35 x 30 ft plus a 150 sq ft strip: 1,050 + 150 = 1,200 sq ft. 1.2 x 9 lb = 10.8 lb, so buy two 7 lb bags or one 20 lb bag and keep the rest for repairs.
Quick reference
| Grass type | New lawn, lb per 1,000 sq ft | Overseeding, lb per 1,000 sq ft | New 5,000 sq ft lawn |
|---|---|---|---|
| Kentucky bluegrass | 3 | 1.5 | 15 lb |
| Tall fescue | 8 | 4 | 40 lb |
| Perennial ryegrass | 9 | 4.5 | 45 lb |
| Fine fescue | 5 | 2.5 | 25 lb |
| Bermuda (hulled) | 2 | 1 | 10 lb |
| Zoysia | 2 | 1 | 10 lb |
How to calculate grass seed
Measure the lawn in feet and multiply length by width for square feet. Seeding rates are published per 1,000 square feet, so divide the area by 1,000 and multiply by the rate for your grass. A 1,000 square foot new tall fescue lawn needs about 8 pounds; overseeding the same lawn needs about 4 pounds.
Blends fall between the single-species rates, so use the bag rate when it differs. The rates here are for fall seeding into prepared soil; dormant or spring seeding loses seed to washout and birds, so pros go 25 to 50 percent heavier. Double the rate does not give a thicker lawn; crowded seedlings damp off and the stand thins by July.
Getting seed to grow
Seed-to-soil contact matters more than quantity. Loosen the top 2 to 3 inches, spread half the seed in each direction, rake it in no deeper than 1/4 inch, then roll. Overseeding means core aerating in two passes or renting a slit seeder; seed dropped on thatch fails. Cover with one bale of wheat straw per 1,000 square feet, thin enough that half the soil shows.
Apply a starter fertilizer such as 18-24-12 at the bag rate. Phosphorus lawn fertilizer is restricted in Minnesota, New Jersey, New York and other states, but starter for new seeding is exempt. Water lightly two or three times a day until germination, then less often and deeper. Mow at 3 to 3-1/2 inches once the grass reaches 4 inches, with a sharp blade.
What this calculator leaves out
The result is seed and starter only. Not included: topsoil or compost for grading, about 1 cubic yard per 325 square feet at 1 inch. Also the aerator or slit seeder rental (typically $80 to $120 a day), straw, and lime if a soil test calls for it. Water runs about 620 gallons per 1,000 square feet a week for 6 weeks.
Mistakes that cost money
- Seeding fescue or bluegrass in April puts seedlings into summer heat and crabgrass; north of the transition zone the window is late August to October.
- Seed dropped on hard ground or thatch never touches soil; core aerate or slit-seed, or rake to bare dirt and drag the seed in.
- Hay instead of wheat straw seeds the lawn with weeds; use one bale of wheat straw per 1,000 sq ft with half the soil showing.
- Weed-and-feed or a crabgrass pre-emergent at seeding stops germination; use a starter fertilizer, and only mesotrione (Tenacity) is labeled for use at seeding.
- A contractor mix is often 30 to 50 percent annual ryegrass that dies the first year; read the seed tag for species and weed seed.
- Watering once a day lets the top 1/4 in dry out and kills sprouted seed; mist two or three times daily until germination.
Key facts
- Tall fescue is seeded at 6 to 8 lb per 1,000 sq ft for a new lawn, one of the heaviest rates because its seeds are large.
- Kentucky bluegrass needs only 2 to 3 lb per 1,000 sq ft because its seed is very small and it spreads by rhizomes.
- Perennial ryegrass germinates in 5 to 10 days, tall fescue in 7 to 14 days, and Kentucky bluegrass in 14 to 30 days.
- One acre is 43,560 sq ft, so a new tall fescue lawn takes about 350 lb of seed per acre.
- Cool-season grasses are best seeded in late summer to early fall; warm-season grasses in late spring.
Frequently asked questions
How much grass seed do I need per square foot?
It depends on the grass. Tall fescue needs about 8 lb per 1,000 sq ft for a new lawn, Kentucky bluegrass about 3 lb, and perennial ryegrass about 9 lb. Overseeding uses about half those amounts.
How much grass seed do I need for an acre?
An acre is 43,560 sq ft. A new tall fescue lawn needs about 350 lb per acre, Kentucky bluegrass about 130 lb, and perennial ryegrass about 390 lb.
Do I need to put straw over grass seed?
On slopes and in full sun, yes: one bale of clean wheat straw per 1,000 sq ft, thin enough that about half the soil shows, holds moisture and stops washout. Do not use hay, which is full of weed seed. On flat, shaded ground a light cover or none is fine if you can water twice a day.
When is the best time to plant grass seed?
Late August through early October for cool-season grasses like fescue, bluegrass and ryegrass. Late spring, once soil temperatures pass 65°F, for Bermuda and zoysia.
Sources and references
- Establishing Turfgrass Areas From Seed (AY-3-W), recommended seeding rates (Purdue University Extension)
- Lawn Establishment (Penn State Extension)
- Seeding and sodding home lawns (University of Minnesota Extension)
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.