Grass seed rates are given in pounds per 1,000 square feet, and they vary more than most people expect: a pound of Kentucky bluegrass contains roughly five to ten times as many seeds as a pound of tall fescue, so it is sown at a fraction of the weight. This calculator measures your lawn, applies a typical rate for the grass and job you choose — or your own rate from the bag — and tells you how many pounds and which bag sizes to buy.
How to use the grass seed calculator
- Choose the area shape and enter its dimensions, or enter a known area.
- Select the grass type.
- Choose New lawn / bare soil or Overseeding.
- Optionally enter a custom seeding rate from the seed label, in lb per 1,000 ft² or g/m².
- Add extra seed for slopes or patchy soil if you want a margin.
Grass seed formula
One pound per 1,000 ft² equals about 4.88 grams per square meter.
Worked example: a new tall fescue lawn
Lawn: 50 × 40 ft = 2,000 ft².
Rate: 7 lb per 1,000 ft² (typical range 5–8).
Seed: 2,000 ÷ 1,000 × 7 = 14 lb (6.35 kg), within a range of 10–16 lb.
Bags: two 7-lb bags, or one 20-lb bag with 6 lb left over for touch-ups.
Typical seeding rates
| Grass | Season | New lawn (lb/1,000 ft²) | Overseeding |
|---|---|---|---|
| Tall fescue | Cool | 5–8 | 3–5 |
| Kentucky bluegrass | Cool | 1½–3 | 1–1½ |
| Perennial ryegrass | Cool | 4–6 | 2–4 |
| Fine fescues | Cool | 3–5 | 2–3 |
| Bluegrass + ryegrass mix | Cool | 3–4 | 1½–2½ |
| Sun & shade mix | Cool | 4–5 | 2–3 |
| Bermudagrass (hulled) | Warm | ½–1½ | ½–1 |
| Zoysiagrass | Warm | 1–2 | ½–1 |
| Centipedegrass | Warm | ¼–1 | ¼–½ |
| Bahiagrass | Warm | 5–10 | 3–5 |
| Buffalograss (treated burs) | Warm | 1½–3 | 1–1½ |
These ranges reflect common university extension recommendations. Unhulled Bermuda seed is sown at about twice the hulled rate, and coated seeds weigh more per seed, so follow the label when it gives a higher figure. St. Augustinegrass is not grown from seed; it is planted as sod or plugs.
Getting seed to grow
- Prepare the soil. Loosen the top couple of inches, rake out debris and level low spots. Seed needs firm contact with soil, not thatch.
- Split the seed into two halves and spread them in perpendicular passes for even coverage.
- Rake lightly and roll so seed is covered by about ⅛–¼ inch of soil.
- Use starter fertilizer if a soil test shows low phosphorus.
- Keep the surface moist with light watering once or twice a day until seedlings appear, then water less often and more deeply.
- Mow when the new grass is about a third taller than its normal mowing height.
Germination takes from about five days for ryegrass to three or four weeks for bluegrass and bahiagrass. If you need cover sooner, or the area is a slope that will wash out, compare the cost of sod with the sod calculator. For thin or compacted soil, the topsoil calculator estimates the cubic yards to bring in first.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
It depends on the grass. Typical new-lawn rates are about 5–8 lb for tall fescue, 1½–3 lb for Kentucky bluegrass, 4–6 lb for perennial ryegrass, 3–5 lb for fine fescues and ½–1½ lb for hulled Bermudagrass per 1,000 ft². Small-seeded grasses have far more seeds per pound, so they need less weight.
How much seed do I need to overseed a lawn?
Overseeding an existing lawn usually takes about half the new-lawn rate, because grass is already present. For tall fescue that is roughly 3–5 lb per 1,000 ft². The exception is winter overseeding of dormant Bermuda with ryegrass, which uses 10 lb or more.
How much grass seed do I need for an acre?
An acre is 43,560 ft², or 43.56 thousand square feet. At 7 lb per 1,000 ft², a tall fescue lawn needs about 305 lb per acre; Kentucky bluegrass at 2 lb needs about 87 lb.
When is the best time to plant grass seed?
Sow cool-season grasses such as fescue, bluegrass and ryegrass in late summer to early fall, when soil is warm and weeds are slowing down; spring is second best. Sow warm-season grasses such as Bermuda, zoysia and centipede in late spring to early summer, once soil temperatures stay above about 65 °F.
Can I use too much grass seed?
Yes. Seeding well above the recommended rate packs seedlings so tightly that they compete for water and light, and crowded stands are more prone to disease. It also wastes money. Use the rate on the seed label as your guide.