Seeding rates are given in pounds of seed per 1,000 square feet, and they vary more than most people expect: a large-seeded bunch grass like tall fescue is sown at several times the rate of tiny-seeded Kentucky bluegrass. This grass seed calculator uses published university extension rates for the most common lawn grasses, for both a new lawn on bare soil and overseeding a thin lawn, and converts them into the pounds and bags you need for your lawn's size.
Seeding too lightly leaves an open, weedy stand, while seeding too heavily, as the University of Massachusetts extension notes, produces crowded, weak seedlings that are slower to mature and more prone to disease. Stick to the range, and if the seed bag lists its own rate, use that with the Custom option. Prefer an instant lawn? See the sod calculator. To feed the new grass, the lawn fertilizer calculator converts a nitrogen rate into pounds of product.
How to use the grass seed calculator
- Enter the length and width of the area to seed. Subtract beds, patios and driveways, or total irregular areas with the square footage calculator.
- Pick the grass type. For blends, use the dominant species or, better, the rate printed on the seed bag (Custom).
- Choose New lawn for bare soil or Overseeding for thickening an existing lawn.
- Enter the bag size you plan to buy to get the number of bags.
- Use the high end of the range if conditions are poor (heavy shade, late season, rough seedbed) and the low end for an ideal, well-prepared seedbed.
Formula
The primary result uses the middle of the recommended range; the range line shows the low and high ends.
Worked example
A new 100 × 50 ft lawn of tall fescue, with 20 lb bags.
- Area: 100 × 50 = 5,000 ft² = 5 × 1,000 ft².
- Rate: 6–8 lb per 1,000 ft² for a new tall fescue lawn (University of Maryland Extension); midpoint 7 lb.
- Seed: 5 × 7 = 35 lb (range 30–40 lb).
- Bags: 35 ÷ 20 = 1.75, so 2 bags.
Overseeding the same lawn with tall fescue at 4 lb per 1,000 ft² would need 20 lb, one bag.
Seeding rates used by this calculator
| Grass | New lawn (lb / 1,000 ft²) | Overseeding (lb / 1,000 ft²) |
|---|---|---|
| Tall fescue | 6–8 | 4 |
| Kentucky bluegrass | 2–3 | 1.5 |
| Fine fescue | 4–5 | 2.5 |
| Perennial ryegrass | 4–6 | 2–3* |
| Bluegrass / ryegrass mix (80:20) | 3–4 | 1.5–2* |
| Bermudagrass, hulled | 1–1.5 | 0.5–0.75* |
New-lawn rates: tall fescue, Kentucky bluegrass and fine fescue from University of Maryland Extension; perennial ryegrass from Virginia Cooperative Extension (SPES-670); the 80:20 mix from University of Illinois Extension; hulled bermudagrass from Virginia Cooperative Extension. Overseeding rates for the first three are UMD's. *Rates marked with an asterisk are about half the new-lawn rate, the same ratio UMD's published figures follow; treat them as estimates and prefer the rate on your seed label.
Timing matters as much as rate
Cool-season grasses (tall fescue, bluegrass, ryegrass, fine fescue) establish best from late summer into early fall in most of the northern and transition-zone U.S., when soil is warm and weed pressure is falling. Warm-season grasses such as bermudagrass are seeded in late spring and early summer once soils are warm. Good seed-to-soil contact, light raking, and keeping the surface moist until seedlings establish matter more than adding extra seed.
Caveats and assumptions
- Rates assume good-quality seed. Low germination or purity on the label calls for a higher rate; check the pure live seed (PLS) information.
- Blends and mixes should be sown at the rate on the bag, which accounts for each species' share.
- Pre-emergent crabgrass herbicides can prevent new grass from germinating. Check the label before seeding a treated lawn.
- Regional recommendations differ. Your state extension service may give rates tuned to your climate.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
It depends on the species: about 6–8 lb of tall fescue, 2–3 lb of Kentucky bluegrass, 4–5 lb of fine fescue or 4–6 lb of perennial ryegrass for a new lawn. Overseeding uses less.
How much grass seed for 5,000 square feet?
For a new tall fescue lawn, about 30–40 lb; for Kentucky bluegrass, about 10–15 lb.
What is the overseeding rate?
Usually about half the new-lawn rate. University of Maryland Extension lists 4 lb of tall fescue, 1.5 lb of Kentucky bluegrass and 2.5 lb of fine fescue per 1,000 ft² for overseeding.
Can I put down too much grass seed?
Yes. Seeding well above the recommended rate creates crowded, weak seedlings that compete with each other and are more susceptible to disease.
Should I use seed or sod?
Seed costs much less and offers more species choice; sod gives an instant lawn and better erosion control on slopes. The sod calculator estimates pallets for the same area.
Sources
- University of Maryland Extension — Lawn Renovation and Overseeding — renovation and overseeding rates
- University of Illinois Extension — Planting a New Lawn — suggested seeding rates for lawn grasses and mixes
- Virginia Cooperative Extension — Maintenance Calendar for Cool-Season Turfgrasses (SPES-670) — seeding rates per 1,000 ft²
- Virginia Cooperative Extension — Establishing Lawns — bermudagrass seeding rates
- UMass Amherst — Seeding Rate Considerations — effects of seeding too lightly or heavily
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.