Grass seed calculator
How much seed you need, by grass species and by whether you are starting from bare soil or thickening an existing lawn. The rate is pre-set per species and editable, because the number on your bag beats any number on a website.
Seed needed
35 lb
1 bag at 50 lb
Rates differ hugely between species because seed size does — see below. Always check the rate printed on your bag: cultivars and coatings shift it, and a coated seed weighs more per viable seed.
Why bluegrass needs a third of what fescue needs
It is not that one grass is hungrier. It is that a pound of one is several times more seeds than a pound of the other.
| Species | Seeds per lb (approx) | New lawn rate | Overseed |
|---|---|---|---|
| Kentucky bluegrass | ~2,200,000 | 2.5 lb | 1.25 lb |
| Tall fescue | ~230,000 | 7 lb | 3.5 lb |
| Perennial ryegrass | ~230,000 | 7 lb | 4 lb |
| Fine fescue | ~550,000 | 4.5 lb | 2.5 lb |
| Bermuda (hulled) | ~1,800,000 | 1.5 lb | 0.75 lb |
| Zoysia | ~1,300,000 | 1.5 lb | 1 lb |
| Centipede | ~400,000 | 0.4 lb | 0.25 lb |
| Bahia | ~170,000 | 7 lb | 4 lb |
Kentucky bluegrass runs to roughly two million seeds in a pound; tall fescue is nearer two hundred thousand. Ten times the seeds per pound is why one needs a third of the weight to reach the same seedling density. Rates are typical published figures and vary by cultivar, coating and supplier — the bag is the authority.
Cool season or warm season
Cool season — seed in autumn
Bluegrass, tall fescue, fine fescue, perennial ryegrass. Late summer into early autumn is the window: soil still warm, air cooling, weed pressure dropping. Spring seeding works but competes with crabgrass and runs into summer heat before it is properly rooted.
Warm season — seed in late spring
Bermuda, zoysia, centipede, bahia. These want soil temperature genuinely up before they do anything, so late spring into early summer. Seeding them early in cold soil is how you end up reseeding.
Common questions
- How much grass seed do I need per 1,000 square feet?
- It depends entirely on the species. Tall fescue and ryegrass typically want around 6–8 lb per 1,000 sq ft on bare soil; Kentucky bluegrass wants 2–3 lb; centipede under half a pound. Using a fescue rate for bluegrass wastes most of the bag, and using a bluegrass rate for fescue gives you a thin lawn.
- Why is the overseeding rate lower?
- Because there is already grass there. You are thickening a stand, not establishing one, so roughly half the new-lawn rate is normal. Overseeding at full rate mostly produces seedlings that compete with each other and die.
- Can I just put down extra seed to be safe?
- It backfires. Overseeded turf germinates too densely, the seedlings compete for water and light, and you end up with weak grass that thins out anyway. Seed is also the expensive part of the job.
- When should I seed?
- Cool-season grasses — bluegrass, the fescues, ryegrass — establish best in late summer to early autumn, when soil is warm and weed pressure is falling. Warm-season grasses like bermuda and zoysia want late spring into early summer once soil temperatures are properly up.
- Does coated seed change the rate?
- Yes. Coatings add weight that is not seed, so a pound of coated seed contains fewer viable seeds than a pound of uncoated. The bag rate accounts for it — which is another reason to use the number on your bag rather than a generic figure.
Laying turf instead? Use the sod calculator for pallets, slabs and waste allowance.