Grass seed is sold by weight, but lawns are covered by rate — so the whole question comes down to one number: how many pounds of seed your square footage needs. For a brand-new lawn, plan on roughly 5–8 lb of seed per 1,000 sq ft. For overseeding a thin lawn, about half that is plenty. The exact figure inside that range is set by the grass type: fine bluegrass seed goes a long way, while larger ryegrass and fescue seed needs more pounds for the same coverage. The table below gives the standard rates, and the worked example after it shows the full calculation on real lawns.
The method never changes: measure the lawn, pick the rate for your grass from the table, multiply. If you only remember one line, make it this one — area ÷ 1,000 × rate = pounds of seed to buy.
Seed rates by grass type
Rates are in pounds per 1,000 sq ft. The new-lawn rate is for sowing bare soil; the overseeding rate is for thickening up a lawn that is already there.
| Grass type | New lawn (lb per 1,000 sq ft) | Overseeding (lb per 1,000 sq ft) |
|---|---|---|
| Kentucky bluegrass | 2–3 | 1–2 |
| Perennial ryegrass | 7–9 | 4–5 |
| Tall fescue | 6–8 | 3–4 |
| Fine fescue | 4–5 | 2–3 |
| Typical lawn mix | 5–8 | 3–4 |
Why the spread? Seed size. A pound of Kentucky bluegrass holds millions of tiny seeds; a pound of tall fescue holds far fewer, much larger seeds — so fescue needs more pounds to put the same number of plants in the ground. Working in metric? A new-lawn rate of about 35 g/m² is roughly equal to 7 lb per 1,000 sq ft, which sits mid-range for most grasses. And if your seed bag prints its own rate, use the bag — it knows the variety in it.
Worked example
Take a lawn 40 ft long by 25 ft wide. Its area is 40 × 25 = 1,000 sq ft, and say you are sowing tall fescue from scratch at 7 lb per 1,000 sq ft. The maths is one line: (1,000 ÷ 1,000) × 7 = 7 lb of seed. A single 10 lb bag covers it, with some to spare.
Scale it up: a 2,000 sq ft lawn in perennial ryegrass at 8 lb per 1,000 sq ft needs (2,000 ÷ 1,000) × 8 = 16 lb. Bags rarely come in 16 lb, so buy a 20 lb bag and keep the spare — you will want it for patching thin spots and the odd bare patch after the first mow. Seed keeps for a year or two in a cool, dry shed, so a surplus is never wasted.
A note on bags: seed is commonly sold in 5, 10, 20 and 50 lb bags. Round your total up to the next bag size rather than down. Running short mid-lawn can leave a visible change in density where the second batch starts, and every lawn needs a little spare seed for repairs.
Measure first
Every rate above is per 1,000 sq ft, so an accurate area is what makes the rest work. Tape the length and width of each rectangular section and multiply; for a lawn with awkward corners, beds or a curve, split it into simpler shapes, measure each piece and add them together — or let the Square Footage Calculator work out the area piece by piece. Ten minutes of measuring beats a second trip to the store.
Seed or sod?
Seed is the budget option: a whole lawn’s worth costs a fraction of the price of sod, and you can choose exactly the grass mix for your shade and soil. The trade is time — weeks of watering and waiting before the lawn can be walked on. Sod is the instant option, laid in a day and usable within a few weeks, at a much higher price. If you are pricing up both, our Sod Calculator turns the same measurements into rolls and pallets, so you can compare like with like.
Sowing basics
Good seed on bad preparation still fails, so give the basics their due. Rake the soil level and firm, removing stones and old thatch. Sow half the seed walking in one direction and half walking across it, so no strip is missed or doubled. Rake it in very lightly, then keep the surface constantly moist until the grass is established — little and often, not one heavy drenching a day. Timing matters more than anything: early autumn is the best season, when the soil is warm, the weeds are fading and the rain helps you. Spring is a good second choice, once the soil has warmed up.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
For a new lawn, 5–8 lb per 1,000 sq ft covers most grasses — less for Kentucky bluegrass (2–3 lb), more for perennial ryegrass (7–9 lb). Check the table above for your grass type, and use the rate on the seed bag if it gives one.
How much seed do I need for overseeding?
About half the new-lawn rate for your grass type — typically 3–4 lb per 1,000 sq ft. You are filling gaps in an existing lawn, not covering bare soil, so a full rate wastes seed and can crowd the grass already there.
When is the best time to sow grass seed?
Early autumn. The soil is still warm enough for fast germination, autumn rain keeps the seedbed moist, and weed pressure is low. Spring is the second choice — sow once the soil has warmed and the worst frosts have passed.
How long does grass seed take to germinate?
It depends on the type: perennial ryegrass is quick at 5–10 days, while Kentucky bluegrass takes 14–30 days. Fescues sit in between, at about 10–20 days. Keep the seedbed moist the whole time — seed that dries out mid-germination often dies.
Estimates only — follow the rate on your seed bag if it differs; seed varieties vary.