Grass Seed Calculator
Work out how many pounds of grass seed your lawn needs at the right rate.
What you'll need to order
- grass seed
- starter fertiliser
- peat moss or seed blanket
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
pounds of seed = (length × width ÷ 1000) × seeding rate
Seeding rates are always quoted per 1,000 sq ft. Rates vary widely by species: tall fescue needs 6 to 8 lb, ryegrass 5 to 7 lb, and Kentucky bluegrass only 2 to 3 lb because its seed is far smaller.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- USDA NRCS Plant Materials Technical Note 2021 — seeding rates per 1,000 sq ft by turfgrass species
Cited to a specific edition on purpose — table numbers and values move between cycles. Confirm against whichever edition is enforced locally.
Worked example
With length 50 ft, width 40 ft, seeding rate 5 lb, this calculator returns 10 lb.
Grass seed by lawn size
Figures below assume width 40 ft × seeding rate 5 lb. Every row here opens the calculator already filled in. Copy that link and the numbers travel with it.
| Length | Grass seed needed (lb) | Lawn area (sq ft) | 50 lb bags (bags) |
|---|---|---|---|
| 20 ft | 4.00 | 800.0 | 0.08 |
| 40 ft | 8.00 | 1,600 | 0.16 |
| 60 ft | 12.00 | 2,400 | 0.24 |
| 80 ft | 16.00 | 3,200 | 0.32 |
| 100 ft | 20.00 | 4,000 | 0.40 |
| 150 ft | 30.00 | 6,000 | 0.60 |
Lawns 40 ft wide, seeded at 5 lb per 1,000 sq ft — a typical new-lawn rate for tall fescue.
How much seed for a new lawn or overseeding?
Each row is a link that fills in the calculator above. Send one and the other end sees the same figures you do.
| Job | Size | Grass seed needed |
|---|---|---|
| Overseeding a small lawn | 40 ft × 25 ft × 3 lb | 3.00 lb |
| New front lawn | 50 ft × 30 ft × 6 lb | 9.00 lb |
| Overseeding a back garden | 60 ft × 40 ft × 3 lb | 7.20 lb |
| Repairing bare patches | 10 ft × 10 ft × 8 lb | 0.80 lb |
| Full quarter-acre lawn | 110 ft × 80 ft × 6 lb | 52.80 lb |
Overseeding uses roughly half the rate of a new lawn. Patch repair uses more, because bare soil loses seed to birds and runoff.
Seeding rates by grass type
| Type | Rate for a new lawn (lb per 1,000 sq ft) | Notes |
|---|---|---|
| Tall fescue | 6.00 | Cool season, drought tolerant |
| Kentucky bluegrass | 3.00 | Fine seed; spreads by rhizomes |
| Perennial ryegrass | 8.00 | Germinates fastest, 5 to 10 days |
| Fine fescue | 5.00 | Shade tolerant, low maintenance |
| Bermuda (hulled) | 2.00 | Warm season; very fine seed |
| Zoysia | 2.00 | Warm season; slow to establish from seed |
Halve these rates for overseeding an existing lawn. Sowing heavier than recommended produces seedlings that compete with each other and thin out within a season.
Frequently asked questions
How much grass seed for 1,000 square feet?
Three to eight pounds depending on species. Tall fescue takes about 6 lb for a new lawn, Kentucky bluegrass 3 lb, and perennial ryegrass 8 lb.
How much grass seed for a quarter acre?
A quarter acre is 10,890 sq ft, so roughly 65 lb of tall fescue at 6 lb per 1,000 — around one and a half 50 lb bags.
When is the best time to seed a lawn?
Late summer to early autumn for cool-season grasses, late spring for warm-season. Autumn seeding gives the seedlings two cool growing seasons before their first summer.
How much grass seed do I need per 1,000 square feet?
It depends on the species. Tall fescue takes 6 to 8 lb, perennial ryegrass 5 to 7 lb, and Kentucky bluegrass just 2 to 3 lb. Halve these figures when overseeding an existing lawn.
What happens if I use too much grass seed?
Seedlings compete with each other for water and light, producing thin, weak grass prone to disease. More seed does not mean a thicker lawn — it usually means a worse one.
How much seed do I need to overseed?
About half the new-lawn rate, since existing turf is already covering the ground. For fescue that means 3 to 4 lb per 1,000 sq ft. Mow short and rake first so the seed reaches soil.
Is seeding cheaper than laying sod?
Considerably — usually a tenth of the cost per square foot. The trade-off is time and risk: sod is a lawn immediately, while seed takes a full season to establish and depends on consistent watering.