How to use the grass seed calculator
- Enter the lawn size (length × width) or the total area. For odd shapes, split the lawn into rectangles and add them.
- Choose your grass type. The calculator uses the middle of the recommended range.
- Choose new lawn or overseeding.
- Enter your bag size to see how many bags to buy.
Grass seed formula
Seed (lb) = Lawn area (ft²) ÷ 1,000 × Seeding rate (lb per 1,000 ft²) Overseeding ≈ ½ of the new-lawn rate 1 lb per 1,000 ft² = 4.88 g per m²
Worked example
A 5,000 ft² new lawn of turf-type tall fescue at 8 lb per 1,000 ft²:
- Seed = 5,000 ÷ 1,000 × 8 = 40 lb
- In 5 lb bags = 8 bags
- For overseeding the same lawn: about 20 lb
Seeding rates by grass type (new lawn)
| Grass | lb per 1,000 ft² | g per m² | Best for |
|---|---|---|---|
| Kentucky bluegrass | 2–3 | 10–15 | Sunny lawns in cool climates |
| Turf-type tall fescue | 6–10 | 29–49 | Heat, drought and wear; transition zone |
| Perennial ryegrass | 7–8 | 34–39 | Fast cover, sports turf, overseeding |
| Fine fescue | 3–6 | 15–29 | Shade and low maintenance |
| Bluegrass + ryegrass mix | 3–4 | 15–20 | Quick-establishing cool-season lawn |
| Bermudagrass (hulled) | 1–2 | 5–10 | Full sun in hot climates |
| Bermudagrass (unhulled) | 4–8 | 20–39 | Cheaper, slower to germinate |
Reading a seed label
A seed bag lists the germination rate and purity. Multiply them to get pure live seed (PLS): 90% purity × 85% germination = 76.5% PLS. A cheap bag with lots of inert matter or weed seed can cost more per pound of live seed than a premium bag. Also check for “coated” seed — the coating can be up to half the weight, so you need more pounds to sow the same number of seeds; the bag will give its own rate.
Some warm-season grasses, such as St. Augustine and most hybrid bermudas and zoysias, are not grown from seed at all — they are planted as sod or plugs. For those, use our Sod Calculator.
Tips for a thick new lawn
- Prepare the soil. Loosen the top 4–6 in, rake out stones and level it. Add topsoil or compost if needed.
- Get good seed-to-soil contact. Rake lightly after spreading and roll with an empty roller.
- Spread in two passes at right angles with a spreader for even cover.
- Keep the top inch moist — water lightly once or twice a day until germination, then water deeper and less often.
- Use a starter fertilizer and hold off on weed killers until you have mowed the new grass a few times.
- First mow when the grass is about one-third taller than its target height.
- Keep foot traffic off the new lawn for about 4–6 weeks while the roots establish.