Formula
Pounds of seed are the net area divided by 1,000, times the rate, times one plus any overlap allowance. An acre is 43,560 square feet, so the per-acre rate is the per-1,000 rate times 43.56. Pure live seed is purity times germination, divided by 100. Bag weight is the target pounds divided by that fraction. Virginia Cooperative Extension’s fall guide is the cool-season table used here: Kentucky bluegrass 1–2, tall fescue 6–8, fine fescue 3–5, perennial ryegrass 3–5. The defaults sit inside those ranges (2, 6, 4, and 4). York’s establishing-lawns sheet separates hulled bermudagrass at 1–1.5 pounds from unhulled at 5–10.
lb = area / 1,000 × rate × (1 + waste)
PLS% = purity × germination / 100
product = target ÷ (PLS% / 100)
Overseed starts at half the new-lawn rate on the form, and you can type over it. University of Maryland lists establishment and overseed side by side: tall fescue 6–8 and 4, Kentucky bluegrass 2–3 and 1.5, fine fescue 4–5 and 2.5. Those are not exactly half of every number in the range. Half is the planning switch; the Maryland table is why a lower rate is the renovation habit. Seed in two directions, each pass at half the rate, is how both Virginia and Maryland describe a uniform spread. York’s sheet covers new seed with straw so about 50 to 75 percent of the soil still shows, about 1.5 to 2 bales per 1,000 square feet. Mixtures follow the bag, because the rate depends on the blend.
Worked examples
Tall fescue, 5,000 ft², 6 lb per 1,000. 30 lb, 0.60 of a 50 lb bag. With 10 percent overlap, 33 lb. Overseed at 3 lb per 1,000 is 15 lb.
Kentucky bluegrass, 2 lb per 1,000, 10,000 ft². 20 lb. PLS 95 × 85. 80.75 percent, 7.43 lb of product per 1,000, 37.15 lb on 5,000 ft².
40 × 25 ft. 6 lb at 6 per 1,000. 50 × 40 minus a 10 × 10 bed. 1,900 ft², 11.4 lb.
Reference
New-lawn starting rates on this page. Edit them. The tag wins.
| Species | Range cited | Default |
|---|---|---|
| Kentucky bluegrass | 1–2 lb (VCE fall); Maryland establishment 2–3 | 2 |
| Turf-type tall fescue | 6–8 lb (VCE fall and Maryland establishment) | 6 |
| Fine fescue | 3–5 lb (VCE); Maryland establishment 4–5 | 4 |
| Perennial ryegrass | 3–5 lb (VCE fall) | 4 |
| Bermudagrass, hulled | 1–1.5 lb hulled (York VCE); VCE spring also lists 0.5–1 | 1 |
| Bermudagrass, unhulled | 5–10 lb unhulled (York VCE) | 5 |
Questions
How much grass seed per 1,000 square feet?
It depends on the species. Virginia Cooperative Extension’s fall guide lists tall fescue at 6 to 8 pounds, Kentucky bluegrass at 1 to 2, and fine fescue and perennial ryegrass at 3 to 5. The bag label can disagree, and it wins.
How much seed for a new lawn?
Use the full new-lawn rate. Five thousand square feet of tall fescue at 6 pounds per 1,000 is 30 pounds, 0.60 of a 50 pound bag.
How much seed for overseeding?
This page starts an overseed at half the new-lawn rate you have selected, and you can edit it. University of Maryland lists turf-type tall fescue overseeding at 4 pounds per 1,000, Kentucky bluegrass at 1.5, and fine fescue at 2.5, next to higher establishment rates.
What is pure live seed?
Purity percent times germination percent, divided by 100. A 95 percent pure lot at 85 percent germination is 80.75 percent PLS. Divide the target pounds by that fraction to get the bag weight.
How do I calculate grass seed for my yard?
Measure the lawn, subtract beds and the driveway, then multiply the net square feet by the rate per 1,000. A 40 by 25 foot rectangle at 6 pounds per 1,000 is 6 pounds.
Why do tall fescue and Kentucky bluegrass use different rates?
The seed is a different size, so a pound holds a different number of plants. Extension tables set the pounds so the stand is thick without the seedlings crowding each other.
How many bags do I need?
Divide the pounds by the bag weight and round up if you have to buy whole bags. Thirty pounds is 0.60 of a 50 pound bag, so one bag covers it with seed left over.
Sources
- Virginia Cooperative Extension, “Fall Into Your Lawn: Establishing Cool-season Turfgrasses.” Kentucky bluegrass 1–2 lb, tall fescue 6–8, fine-leaf fescue 3–5, perennial ryegrass 3–5, per 1,000 sq ft. Seed in two directions at half the rate each way. Mixtures follow the bag.
- University of Maryland Extension, “Grass Seed” and “Lawn Renovation and Overseeding.” Establishment: tall fescue 6–8, Kentucky bluegrass 2–3, fine fescue 4–5. Overseeding: 4, 1.5, and 2.5 lb per 1,000.
- Virginia Cooperative Extension, York County, “Establishing Lawns.” Hulled bermudagrass 1–1.5 lb, unhulled 5–10 lb per 1,000. Straw mulch at about 1.5–2 bales per 1,000 so 50–75 percent of the soil still shows. A VCE spring note also lists bermudagrass at 0.5–1 lb.
- LSU AgCenter, “Pure Live Seed Calculation.” PLS is purity times germination. Divide the pounds of PLS you want by that fraction to get bag weight.