"How much grass seed for my lawn?" sounds like it should have one answer. It doesn't — and the surprise is that it depends more on the grass than the lawn. Using the seeding rates a grass-seed calculator ships (typical U.S. cooperative-extension figures), the amount you need swings 5.3× from one species to the next.
The seeding rate runs from 1.5 to 8
Seeding rate is measured in pounds per 1,000 square feet, and it's a property of the grass, not the yard:
| Grass (new lawn) | lb per 1,000 sq ft |
|---|---|
| Perennial ryegrass | 8 |
| Tall fescue | 7 |
| Generic / mixed | 5 |
| Kentucky bluegrass | 2.5 |
| Bermuda | 1.5 |
That's a 5.3× gap between perennial ryegrass and Bermuda, with the others across the middle.
What it means for a real lawn
Multiply the rate by your area in thousands of square feet and the gap becomes concrete. On the same 5,000 sq ft lawn:
- Perennial ryegrass → 40 lb
- Tall fescue → 35 lb
- Kentucky bluegrass → 12.5 lb
- Bermuda → 7.5 lb
Same yard, same job, five times the seed. Buy for the wrong grass and you either waste half a bag or sow too thin to fill in.
One bag, wildly different coverage
Flip it around and it's sharper still. A single 20 lb bag covers about 13,333 sq ft of Bermuda — but only 2,500 sq ft of perennial ryegrass, a 5.3× difference from the identical bag weight. Which is why "one bag does an average lawn" is useless advice: the bag doesn't know what grass is in it.
Why: seed size, not area
The reason is seed size. A good lawn is set by seeds per square foot, not pounds — and Bermuda seed is so small that a pound holds a vast number of them, while ryegrass seed is many times heavier, so a pound holds far fewer. Same target density, very different weight. That single fact is the whole 5.3× spread. (And overseeding an existing lawn uses about half the new-lawn rate, since you're thickening turf rather than covering bare soil.)
Reproduce it
Every figure is the rate table times one line of arithmetic:
const RATE = { 'perennial-rye': 8, 'tall-fescue': 7, 'generic': 5,
'kentucky-bluegrass': 2.5, 'bermuda': 1.5 } // lb / 1,000 sq ft
const pounds = (rate, areaSqFt) => rate * (areaSqFt / 1000)
// pounds(8, 5000) = 40 lb rye · pounds(1.5, 5000) = 7.5 lb Bermuda
The rates are mid-range extension figures — a starting point; always follow your seed bag's label. The grass-seed calculator does this for your area and grass (with a rate override), in the browser.
Originally published on LK Forge.
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