Short answer: pounds of seed = lawn square feet ÷ 1,000 × the seeding rate for your grass. A new 5,000 sq ft tall fescue lawn at 6 to 8 lb per 1,000 sq ft needs 30 to 40 lb of seed. That is four 10 lb bags.

Seeding rates by grass type

Rates are pounds of seed per 1,000 square feet, as the cited extension source gives them.

Grass	New lawn	5,000 sq ft needs	Source
Tall fescue (turf-type)	6–8 lb	30–40 lb	Penn State
Kentucky bluegrass	2–3 lb	10–15 lb	Penn State
Perennial ryegrass	4–5 lb	20–25 lb	Penn State
Fine fescues	4–5 lb	20–25 lb	Penn State
Bluegrass, fine fescue and ryegrass mix	3–4 lb	15–20 lb	Penn State
Bluegrass and ryegrass mix	2–3 lb	10–15 lb	Penn State
Bermudagrass (common, hulled)	½–1 lb	2.5–5 lb	UT Extension
Zoysiagrass (Zoysia japonica)	½–3 lb	2.5–15 lb	UT Extension
Centipedegrass	½–3 lb	2.5–15 lb	UT Extension

The Penn State sun mix is 40-60% Kentucky bluegrass, 20-40% fine fescue and 10% perennial ryegrass by weight. The two-way mix is 80-90% bluegrass and 10-20% ryegrass. UT Extension says unhulled Bermudagrass needs double the hulled rate.

Overseeding rates

Penn State gives 4 to 6 lb of perennial ryegrass per 1,000 sq ft for overseeding or renovation. K-State Research and Extension says to use about half the new-lawn rate when overseeding tall fescue and Kentucky bluegrass, which works out to 3 to 4 lb and 1 to 1.5 lb per 1,000 sq ft. Our sources give no overseeding rate for the other grasses. For those, the calculator uses a share of the new-lawn rate that you set. It starts at 50%, which is our assumption, not a sourced figure. Raise it toward 100% if the lawn is thin or bare.

When to sow

Grass group	Best time	Source
Cool-season (fescues, bluegrass, ryegrass)	Late summer is optimum in most of Pennsylvania. Mid-spring to early fall can work.	Penn State
Cool-season, South Carolina	Mid to late September	Clemson HGIC
Warm-season (Bermuda, zoysia, centipede), South Carolina	Target May 1 to 14	Clemson HGIC

Clemson warns that warm-season seed sown too early can rot in cold soil. Seed sown later can dry out in summer heat. UT Extension notes that cool-season seed germinates fastest when air temperatures cycle between about 59 and 82°F.

Seed-to-soil contact and watering

Rake it in. Clemson says to mix the seed into the top ¼ inch of soil with a rake.
Roll it. Use a light or empty water-ballast roller to press seed into the soil, per Clemson and Penn State.
Mulch if needed. Clemson suggests weed-free straw where erosion or drying is a concern. One 60 to 80 lb bale covers about 1,000 sq ft.
Water right away. Clemson advises light watering two or three times a day for about two to three weeks. Keep the seedbed moist, not soaked.
Then water deeper. As roots grow, water less often but longer. UT Extension suggests about ½ inch every two to three days.

Common questions

Can I just put down more seed for a thicker lawn?

Our sources give ranges, not a reason to go past them. Stay within the listed range, and use the high end for bare or thin areas.

Should I follow the bag label or this calculator?

Follow the label for blended bags, since each blend has its own mix. Use this calculator to check the label and to plan how many bags to buy.

How do I measure an odd-shaped lawn?

Split it into rectangles, work out each one's square feet, and add them. Enter the total in the square feet box.

Do I fertilize when I seed?

Fertilizer timing depends on your grass type. See when to fertilize your lawn, then size the amount with our lawn fertilizer calculator.

How much grass seed do I need?

1. Your lawn and seed

2. How much seed to buy