Grass Seed Calculator
Tall fescue goes down at 7 lb per thousand square feet and bermuda at 1.5, so any grass seed calculator that gives you one number for everything is wrong for most people. This one takes the rate from the species you are actually sowing, at the new-lawn or overseeding rate.
Your result
| Grass | Rate | Pounds | Seed cost |
|---|---|---|---|
| Tall fescue (yours) | 7 | 35 | $140 |
| Kentucky bluegrass | 2.5 | 12.5 | $100 |
| Perennial ryegrass | 7.5 | 37.5 | $131 |
| Fine fescue | 4.5 | 22.5 | $113 |
| Bermuda, hulled | 1.5 | 7.5 | $68 |
| Zoysia | 1.5 | 7.5 | $90 |
| Centipede | 0.4 | 2 | $60 |
| Bahia | 8 | 40 | $200 |
What to buy
35 lb of tall fescue seed for 5,000 sq ft, plus 7 bales of straw
1 bag of 50 lb covers it, with 15 lb spare for patching. Straw goes on thin enough to still see soil through it, which is about 7 bales here.
- Rate per acre
- 7 lb per 1,000 sq ft is 304.9 lb an acre, since an acre is 43.56 thousand square feet. Large jobs are usually quoted the second way.
- Why not just sow it heavier
- Overseeding the rate crowds the seedlings, and crowded grass competes with itself for water and light rather than filling in. It also raises the disease risk in the first month. Twice the seed does not give you twice the lawn, it gives you a thinner one and a bigger bill.
- How this is worked out
- 5,000 sq ft ÷ 1,000 = 5 × 7 lb = 35 lb of tall fescue at the new lawn rate
Calculate how much grass seed you need
Divide the lawn area by 1,000, then multiply by the seeding rate for your species. That’s the whole calculation, and the only hard part is knowing which rate to use.
A 5,000 sq ft lawn is 5 thousand square feet. Sown new with tall fescue at 7 lb that comes to 35 lb of seed. Overseeding the same lawn at 3.5 lb needs 18 lb, and the same lawn in bermuda would take just 7.5 lb.
Measure the grass and nothing else. Beds, the drive and the house footprint all come out of the total, because seed spread over a driveway is simply wasted. On a typical suburban plot the mowable area is barely half the lot.
Round up to the next bag rather than buying exactly what the arithmetic says. Seed keeps for a couple of seasons in a cool dry place, and having a few pounds spare for patching bare spots the following spring is worth more than the few dollars saved by cutting it fine.
Seeding rate by grass type
The spread between species is the thing most calculators ignore. Centipede goes down at 0.4 lb per thousand and bahia at 8, a factor of twenty, because the seed itself differs that much in size.
| Grass | Season | New lawn | Overseed | Germination |
|---|---|---|---|---|
| Tall fescue | Cool | 7 | 3.5 | 7–12 days |
| Kentucky bluegrass | Cool | 2.5 | 1.25 | 14–30 days |
| Perennial ryegrass | Cool | 7.5 | 3.75 | 5–10 days |
| Fine fescue | Cool | 4.5 | 2.25 | 7–14 days |
| Bermuda, hulled | Warm | 1.5 | 0.75 | 7–15 days |
| Zoysia | Warm | 1.5 | 0.75 | 14–21 days |
| Centipede | Warm | 0.4 | 0.2 | 14–21 days |
| Bahia | Warm | 8 | 4 | 14–28 days |
Cool-season grasses fill the northern half of the country and the transition zone. Warm-season grasses take the south, go dormant and brown in winter, and are sown at far lower rates because the seed is tiny. Sowing a warm-season rate for a cool-season grass leaves a lawn that never thickens up.
Germination time matters as much as rate when you are planning. Ryegrass is up in 5–10 days and Kentucky bluegrass can take 14–30, which is why blends often pair them: the ryegrass holds the soil while the bluegrass establishes underneath it.
New lawn against overseeding
Overseeding uses about half the new-lawn rate, because you are filling gaps in an existing stand rather than covering bare soil. Tall fescue drops from 7 lb to 3.5, bluegrass from 2.5 to 1.25.
| Grass | New lawn | Overseed | Seed cost, new |
|---|---|---|---|
| Tall fescue | 35.0 lb | 17.5 lb | $140 |
| Kentucky bluegrass | 12.5 lb | 6.3 lb | $100 |
| Perennial ryegrass | 37.5 lb | 18.8 lb | $131 |
| Fine fescue | 22.5 lb | 11.3 lb | $113 |
| Bermuda, hulled | 7.5 lb | 3.8 lb | $68 |
| Zoysia | 7.5 lb | 3.8 lb | $90 |
| Centipede | 2.0 lb | 1.0 lb | $60 |
| Bahia | 40.0 lb | 20.0 lb | $200 |
The two jobs also want different preparation. A new lawn needs bare, raked soil and constant moisture for the first two weeks. Overseeding wants the existing turf cut short and scarified or core-aerated first, because seed sitting on thatch never reaches soil and never germinates.
Timing differs too. Overseeding works best a few weeks earlier than a new lawn, while the existing turf is still growing strongly enough to knit the new seedlings in before the season ends.
Look down the cost column and the species choice matters more than the area does. The same lawn ranges from under $60 to over $200 depending purely on what you sow.
Seed needed per 1,000 sq ft and per acre
Bags are labeled per 1,000 sq ft because that is the working unit for a domestic lawn. For anything large, the per-acre figure is what a supplier quotes, and the conversion is a straight multiply by 43.56.
| Grass | Lb per 1,000 sq ft | Lb per acre | 50 lb bag covers |
|---|---|---|---|
| Tall fescue | 7 | 305 | 7,143 sq ft |
| Kentucky bluegrass | 2.5 | 109 | 20,000 sq ft |
| Perennial ryegrass | 7.5 | 327 | 6,667 sq ft |
| Fine fescue | 4.5 | 196 | 11,111 sq ft |
| Bermuda, hulled | 1.5 | 65 | 33,333 sq ft |
| Zoysia | 1.5 | 65 | 33,333 sq ft |
| Centipede | 0.4 | 17 | 125,000 sq ft |
| Bahia | 8 | 348 | 6,250 sq ft |
An acre is 43.56 thousand square feet, so tall fescue at 7 lb per thousand is 305 lb an acre. That’s six or seven 50 lb bags for a single acre of new lawn, which is the point where buying by the pallet starts to make sense.
The last column is the useful one in a store. A 50 lb bag of bermuda covers over 33,333 sq ft while the same bag of tall fescue covers about 7,143, so comparing bag prices without comparing coverage tells you very little.
How much topsoil to add first
On decent existing soil, none. Rake the surface to break the crust so seed can make contact and sow straight onto it. Adding topsoil over good ground buries what is already there and gains nothing.
Where the ground is compacted, stony or builder’s subsoil, spread 2 to 3 in of screened topsoil and rake it level. For 1,000 sq ft that is 6.2 to 9.3 cubic yards, and for a 5,000 sq ft lawn it comes to 30.9 to 46.3 yards. The topsoil calculator handles the ordering side of that, including what will fit in a pickup.
Whatever you put down, firm it before seeding. Loose topsoil settles unevenly after the first heavy rain and takes the new grass with it, leaving a lawn full of dips that are difficult to correct once it has rooted.
Straw, watering and the first month
Straw holds moisture and stops seed washing off a slope. One bale covers about 800 sq ft, so a 5,000 sq ft lawn takes around 7 bales. Spread it thin enough to still see soil through it, because a thick blanket smothers the seedlings it was meant to protect.
Use straw rather than hay. Hay is cut with the seed heads still on it and you’ll be weeding the result for years. Clean wheat straw is the standard, and it breaks down into the soil rather than needing raking off.
Water lightly and often until germination, then less often and more deeply. The top half inch has to stay damp for the whole germination window, which for bluegrass at 14–30 days means three weeks of not letting it dry out once. That single requirement is what most failed seedings come down to.
What grass seed costs
Between $4 and $30 a pound depending on species. Ryegrass and tall fescue are cheapest, bluegrass and the warm-season grasses cost considerably more per pound, though they go down at lower rates.
Rate and price pull against each other, so compare the finished cost rather than the shelf price. Centipede is $30 a pound against $4 for tall fescue, but at 0.4 lb per thousand against 7 the 5,000 sq ft lawn actually costs $60 in centipede and $140 in fescue.
Be wary of very cheap mixes. They’re usually mostly annual ryegrass, which comes up fast, looks convincing for one season and then dies, leaving you to seed the same lawn again. Check the label for the percentage of each species and the weed seed content before comparing anything on price.
Grass seed questions
How much grass seed do I need per 1,000 sq ft?
It depends entirely on the species. Tall fescue goes down at 7 lb per 1,000 sq ft for a new lawn, Kentucky bluegrass at 2.5 and bermuda at 1.5. Overseeding an existing lawn uses roughly half the new-lawn rate.
How much grass seed per acre?
Multiply the rate per 1,000 sq ft by 43.56, since that is how many thousand square feet an acre holds. Tall fescue works out at about 305 lb an acre and bermuda nearer 65 lb.
How much grass seed do I need for 5,000 square feet?
About 35 lb of tall fescue for a new lawn, or 18 lb to overseed. For Kentucky bluegrass the same lawn takes 13 lb, and for bermuda only 7.5 lb.
Can I use too much grass seed?
Yes, and it is a common mistake. Seedlings crowded together compete for water and light, so the lawn comes in thinner rather than thicker, and dense stands are more prone to damping off in the first few weeks. Sow the rate and no more.
What is the overseeding rate for grass seed?
About half the new-lawn rate. Tall fescue drops from 7 to 3.5 lb per 1,000 sq ft and Kentucky bluegrass from 2.5 to 1.25. You are filling gaps in an existing stand rather than establishing one from bare soil.
When should I plant grass seed?
Late summer into early fall for cool-season grasses, which is the single best window because soil is warm and weed pressure is falling. Warm-season grasses go down in late spring once soil holds above 65°F. Spring seeding of cool-season grass works but fights crabgrass all summer.
How much topsoil do I need before seeding?
Two to three inches over compacted or poor ground, which for 1,000 sq ft is about 6.2 to 9.3 cubic yards. On decent existing soil you need none, just raking to break the surface so seed makes contact.
Do I need straw over grass seed?
It helps on bare soil by holding moisture and stopping seed washing away. One bale covers about 800 sq ft laid thin enough to still see soil through it. Use clean straw rather than hay, which carries weed seed.