How much grass seed you need — by grass type, new lawn or overseeding
A new lawn (bare soil) uses the full rate; overseeding an existing lawn uses about half. The rate also depends on the grass type you pick above.
Tip: the rate printed on your seed bag wins — premium and coated seed differ. This uses typical published new-lawn rates and halves them for overseeding.
Seed needed
—
enter size
Seeding rate
Grass Seed Calculator — guide & how to use
Estimates only. Always confirm the seeding rate printed on your specific seed bag — rates vary by variety, blend, and seed coating. Real results depend on soil prep, watering, and timing. All math runs privately in your browser.
What it does
This grass seed calculator turns your lawn area and grass type into the
pounds of seed to buy — for either a brand-new lawn (bare soil) or for
overseeding an existing lawn. It uses the real published seeding rate per 1,000 sq ft
for each grass type, halves it automatically for overseeding, lets you add a waste buffer, and tells you
how many bags to grab. The most common question — "how much grass seed do I need?" —
answered correctly by type, not with one generic number.
How to use it
Pick your grass type (or choose "Custom rate" and enter the lb/1,000 sq ft from your bag).
Choose the job: New lawn (full rate) or Overseed (half rate).
Enter your lawn size — rectangle, circle, or a direct square-footage you already measured.
Pick your bag size, and optionally turn on a waste allowance.
Read the total pounds, the bag count, and the seeding rate used.
How the math works
Area = length × width (rectangle), π × (diameter ÷ 2)² (circle), or your direct sq ft.
Rate = the grass type's new-lawn rate (lb per 1,000 sq ft). For overseeding, the rate is halved.
Seed pounds = rate × area ÷ 1,000.
Waste (if on): multiply by (1 + waste% ÷ 100).
Bags = seed pounds ÷ bag size, rounded up (you can't buy a partial bag).
Worked example
A 50 ft × 40 ft lawn (2,000 sq ft) of tall fescue, new lawn, waste off:
Tall fescue new-lawn rate ≈ 7 lb / 1,000 sq ft.
Seed = 7 × 2,000 ÷ 1,000 = 14 lb.
At 20 lb/bag → 1 bag covers it (14 ÷ 20 = 0.7, rounded up).
Switch to Overseed and the rate halves to 3.5 lb/1,000 → 7 lb of seed.
Typical new-lawn seeding rates
Grass type
New lawn (lb / 1,000 sq ft)
Overseed (≈ half)
Kentucky bluegrass
2–3
1–1.5
Tall fescue
6–8
3–4
Perennial ryegrass
5–6
2.5–3
Fine fescue
1–2
0.5–1
Bermuda
1–2
0.5–1
Zoysia
1–2
0.5–1
Centipede
0.25–0.5
—
Ranges from common university extension and seed-supplier guidance. Your specific bag rate always overrides these defaults.
Accuracy notes & assumptions
This is an estimate. Seeding rate varies by variety, blend, and coating — read your bag.
Overseeding uses ~half the new-lawn rate because existing turf already covers most ground.
Don't over-seed. Too much seed crowds seedlings; they compete and thin out.
Timing & prep matter more than a few ounces of seed. Cool-season grasses go down in early fall; warm-season in late spring. Good soil contact and consistent moisture drive germination.
Common mistakes this avoids
Using one generic seed rate for every grass — fescue needs ~4× the seed of Bermuda.
Seeding a thin existing lawn at full new-lawn rate (wasteful) instead of the overseed rate.
Forgetting that rates are per 1,000 sq ft, not per square foot or per acre.
Rounding bags down and coming up short on the last patch.
How to embed this tool on your website
Frequently asked questions
How much grass seed do I need per square foot?
Seed is rated per 1,000 sq ft and depends on grass type: ~2–3 lb/1,000 for Kentucky bluegrass, 6–8 lb for tall fescue, 5–6 lb for perennial rye, 1–2 lb for Bermuda. Overseeding uses about half. Multiply the rate by area ÷ 1,000.
What's the difference between new-lawn and overseeding rates?
A new lawn over bare soil needs the full rate; overseeding into existing turf uses about half because the ground is already mostly covered. This tool switches the rate when you pick New lawn vs. Overseed.
How many pounds for 1,000 square feet?
By type, for a new lawn: ~2–3 lb KBG, 6–8 lb tall fescue, 5–6 lb perennial rye, 1–2 lb Bermuda. Overseed uses about half. Check your bag for the exact rate.
Should I add extra for waste?
A 5–15% buffer covers edges, wind, and birds. Lean high for rough or sloped ground. Don't massively over-seed — crowded seedlings thin out.
Is it really free?
Yes — 100% free and everything runs in your browser. It's an estimate; confirm the rate on your seed bag.