Lawn
Grass Seed Calculator
Seeding rates differ by species by a factor of twenty, bermudagrass wants 1 lb per 1,000 sq ft, perennial ryegrass wants 8. Pick your grass and whether you're starting fresh or overseeding.
Updated
Lawn area to seed
Measure only the grass. Exclude beds, driveways, and the house footprint.
Area = length × width
Seed selection
Deep roots make it the most drought-tolerant cool-season option. Bunch-type, so thin areas need reseeding rather than filling in on their own.
Your bag's printed rate always beats a generic species figure. Enter it here.
Varies widely by cultivar and blend quality.
Enter your lawn size to see how much seed you need.
Which grass should I plant?
Tell the assistant your location, sun exposure, and how the lawn gets used, and it will suggest species and a seeding plan. Seed quantities stay exactly as calculated.
Written by AI from the figures above. The quantities themselves are calculated deterministically and are never generated by AI. Check anything consequential, permits, utility locates, and chemical labels especially, before acting on it.
How this is calculated
The calculation
Seeding rates are published per 1,000 square feet, so the math is your area divided by 1,000, multiplied by the rate for your species.
The rate itself is the part that matters. Seed size drives it: bermudagrass seed is tiny and a single pound contains close to two million seeds, while ryegrass seed is large and a pound holds around a quarter million. Both aim for a similar number of seeds per square inch of soil, the weight differs because the seeds do.
pounds of seed = (area in sq ft ÷ 1,000) × rate per 1,000 sq ft
New lawn vs overseeding
Overseeding uses roughly half the new-lawn rate. On bare ground every seed has a place to land; in existing turf most of the ground is already occupied, and seed that lands on grass blades rather than soil never germinates.
Seeding heavier than the recommended rate does not give you a thicker lawn. It gives you seedlings competing with each other for water and light, and a stand that thins out badly under its first summer stress. This is one of the most common self-inflicted lawn problems.
| Grass | New lawn | Overseeding | Germination |
|---|---|---|---|
| Kentucky bluegrass | 2–3 | 1–2 | 14–30 days |
| Tall fescue | 6–8 | 4–6 | 7–14 days |
| Perennial ryegrass | 6–9 | 4–6 | 5–10 days |
| Fine fescue | 4–5 | 3–4 | 7–14 days |
| Bermudagrass (hulled) | 1–2 | 1–2 | 7–21 days |
| Zoysiagrass | 1–2 | — | 14–28 days |
| Centipedegrass | ¼–½ | — | 14–28 days |
| Bahiagrass | 6–10 | 4–6 | 14–28 days |
| Buffalograss | 2–4 | — | 14–30 days |
Timing beats rate
Seeding at the right time of year matters more than getting the rate exactly right. Cool-season grasses go down in late summer to early autumn, the soil is still warm, the weeds are slowing down, and the seedlings get a full autumn plus a spring before their first summer.
Warm-season grasses go down in late spring to early summer, once soil temperature is reliably above 65 °F. Seeding warm-season grass in autumn wastes the seed.
Spring seeding of cool-season grass works but is second best: the new grass has weeks rather than months to establish before summer heat, and pre-emergent crabgrass control has to be skipped or it will kill your seedlings too.
Worked example
Overseeding a thin tall fescue lawn
A 6,500 sq ft lawn being overseeded with tall fescue in early September.
- Area in thousands
- 6,500 ÷ 1,000 = 6.5
- Overseed rate (midpoint)
- 5 lb per 1,000 sq ft
- Seed needed
- 6.5 × 5 = 32.5 lb
- Bag sizes
- One 20 lb plus one 20 lb bag, or a single 50 lb bag
About 33 lb of seed. Aerate first, seed needs soil contact, and core aeration is the cheapest way to get it into an established lawn.
Frequently asked questions
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OpenGuides that go deeper
- How Often Should You Overseed a Lawn?Overseeding isn’t a yearly chore for everyone. Here’s how to decide if, when, and how much to overseed,plus the steps that actually matter.
- How to Know If Your Grass Seed Is Still Worth UsingGrass seed loses its punch with time and poor storage. Here’s how to check if your old seed will still sprout, what the label really means, and when to just buy fresh.
- Starter Fertilizer for New Grass: What Most Homeowners Get WrongStarter fertilizer can jumpstart new grass, but using it wrong wastes money or breaks the law. Here’s what to know before you spread.
- Perennial Ryegrass: Fast Green-Up, Smart Uses, and Where It Falls ShortPerennial ryegrass seed is your shortcut to a green lawn,if you use it right. Here’s how to seed, blend, and care for it, plus where it works and where it fizzles.