The rule
Seed (lb) = lawn area (sq ft) ÷ 1,000 × seeding rate (lb per 1,000 sq ft)
Two numbers decide the answer: the size of the lawn and the rate for your grass. The rate is printed on the seed bag. If you are still choosing seed, these are the typical new-lawn rates from extension and seed-industry guides:
| Grass | New lawn, lb per 1,000 sq ft | Per square foot |
|---|---|---|
| Tall fescue | 6–8 | 0.006–0.008 lb (about 0.1–0.13 oz) |
| Kentucky bluegrass | 2–3 | 0.002–0.003 lb (about 0.03–0.05 oz) |
| Perennial ryegrass | 5–8 | 0.005–0.008 lb (about 0.08–0.13 oz) |
| Fine fescue | 3–5 | 0.003–0.005 lb (about 0.05–0.08 oz) |
| Bermudagrass, hulled | 1–2 | 0.001–0.002 lb (about 0.02–0.03 oz) |
| Zoysiagrass | 1–2 | 0.001–0.002 lb (about 0.02–0.03 oz) |
To convert pounds to ounces, multiply by 16. Per-square-foot numbers are tiny, which is why everyone quotes rates per 1,000 sq ft instead.
Step by step
- Measure the lawn. Length × width for each rectangle, and add them. Leave out the house, driveway, patio and beds. The lawn area calculator handles circles, triangles and cut-outs.
- Divide by 1,000. A 3,400 sq ft lawn is 3.4.
- Pick the rate. New lawn on bare soil, or overseeding an existing lawn at roughly half the rate. Use the bag’s number when you have it.
- Multiply. 3.4 × 7 lb (tall fescue, new lawn) = 23.8 lb.
- Round up to bags. 23.8 lb is five 5 lb bags, four 7 lb bags, or one 20 lb bag plus one 5 lb bag.
Chart: seed for common lawn sizes
New-lawn rates at the middle of each range. For overseeding, halve the figures.
| Lawn area | Tall fescue (7 lb) | Perennial rye (6.5 lb) | Fine fescue (4 lb) | Bluegrass (2.5 lb) | Bermuda (1.5 lb) |
|---|---|---|---|---|---|
| 100 sq ft (10 × 10 patch) | 0.7 lb | 0.65 lb | 0.4 lb | 0.25 lb | 0.15 lb |
| 500 sq ft | 3.5 lb | 3.3 lb | 2 lb | 1.25 lb | 0.75 lb |
| 1,000 sq ft | 7 lb | 6.5 lb | 4 lb | 2.5 lb | 1.5 lb |
| 2,500 sq ft | 17.5 lb | 16.3 lb | 10 lb | 6.25 lb | 3.75 lb |
| 5,000 sq ft | 35 lb | 32.5 lb | 20 lb | 12.5 lb | 7.5 lb |
| 1/4 acre (10,890 sq ft) | 76 lb | 71 lb | 44 lb | 27 lb | 16 lb |
| 1/2 acre (21,780 sq ft) | 152 lb | 142 lb | 87 lb | 54 lb | 33 lb |
| 1 acre (43,560 sq ft) | 305 lb | 283 lb | 174 lb | 109 lb | 65 lb |
A quarter-acre lot is not a quarter acre of lawn. Once the house, driveway and beds are out, the grass is often half the lot or less, so measure the grass itself.
Two worked examples
Patching bare spots. Three dead patches, roughly 6 × 4 ft, 5 × 5 ft and a circle 4 ft across. That’s 24 + 25 + 12.6 = 61.6 sq ft. At a tall fescue new-lawn rate of 7 lb per 1,000 sq ft: 0.0616 × 7 = 0.43 lb, under half a pound. A small 3 lb bag will cover it several times over, so save the rest in a cool, dry place for the next repair.
Reseeding a whole backyard. A backyard of 70 × 45 ft with a 12 × 16 ft patio inside it. Grass area: 3,150 − 192 = 2,958 sq ft. With a sun and shade mix at the 5 lb mid-range rate: 2.958 × 5 = 14.8 lb. Three 5 lb bags (15 lb) just cover it; one 20 lb bag leaves some for touch-ups next season. If the bag says 4 lb per 1,000 sq ft, the answer drops to 11.8 lb.
What a bag of grass seed costs
We don’t quote prices, because they swing with the grass, the brand, the bag size and the store. To compare bags fairly, turn each into cost per 1,000 sq ft of new lawn:
Bag price ÷ (bag weight ÷ new-lawn rate)
A bag of a fine-seeded grass such as bluegrass covers far more ground per pound than tall fescue, so a higher bag price can still work out cheaper per square foot. Coated seed needs more pounds for the same coverage, so compare it with its own label rate.
Getting more lawn from the same seed
- Seed into loosened, raked soil, not onto hard ground or thatch.
- Spread in two passes at right angles.
- Rake lightly and roll so seed is pressed into the soil.
- Keep the surface moist until seedlings are mowing height.
- Seed at the right time of year for your grass (early fall for cool-season, late spring to early summer for warm-season).
The rates above are typical ranges. Your seed bag's own rate takes priority, because seed size, coating and mix vary from product to product.
Questions people ask
- How much grass seed do I need per square foot?
- Between about 0.001 and 0.008 lb per square foot for most lawn grasses, which is the per-1,000 sq ft rate divided by 1,000. Tall fescue at 7 lb per 1,000 sq ft is 0.007 lb, or about 0.11 ounces, per square foot.
- How much grass seed do I need for 1,000 square feet?
- For a new lawn, about 6 to 8 lb of tall fescue, 2 to 3 lb of Kentucky bluegrass, 5 to 8 lb of perennial ryegrass or 1 to 2 lb of hulled Bermuda. Overseeding takes roughly half as much.
- How many bags of grass seed do I need?
- Work out the pounds first, then divide by the bag weight and round up. 21 lb of seed is exactly three 7 lb bags. A single 20 lb bag would be a pound short, so you would need a small bag on top.
- How much is a bag of grass seed?
- It depends on the grass, the bag size, whether the seed is coated and where you buy it. Compare bags by price per 1,000 sq ft covered at the new-lawn rate, not by bag price, since a cheap bag of a heavy seed covers less ground.
- Can I just use more seed to get a thicker lawn faster?
- A little extra on bare spots is fine, but doubling the rate crowds seedlings, which then compete for water and light and are more likely to get disease. Good soil contact and steady moisture matter more.